Or is there a way to strike a balance between thematic naming and realistic naming?
Thematic: When the name relates to the character directly. Example: someone who only wears black clothes has the surname Sable, which means "black".
Realistic: What a character from a particular place and time is likely to have as a name based on statistics. Example: the common surnames in the United States are Smith, Brown, Jones, etc
When naming a character, is thematic naming or realistic naming more important?
Naming conventions are entirely discretionary and depend largely on authorial intent and reader demographics/genre expectations.
Serious literary works might place more of an emphasis on historical accuracy, for instance, so the author might avoid any sort of anachronistic nomenclature that undermines their work's authenticity. They might reproduce a realistic name based on the conventions of the culture, language, region, occupation, time period and social status of their character.
But realism doesn't automatically sacrifice symbolism and naming motifs. Many common naming attributions are already naturally denotative. Surnames can symbolize occupation (Smith/Tailor/Cotter/Carpenter/Butcher), region (lexical suffixes), family dynamics (patriarchal/matriarchal/tribal), or even status. Monikers, nicknames, aliases, pen-name handles and titles work in the same manner, they are naturally-occurring or culturally-appropriate aptronyms that reflect the personal attributes of the character.
The literary customs surrounding naming motifs are just as important and serve their own purpose. Often, these sorts of names hark back to a time when name-punning and alliteration were fashionable satirical devices used to ridicule, hyperbolize and poke fun. Charles Dickens and JK Rowling both capitalized on this sort of humor, allowing social commentary and stereotyping without being overly subversive. Naming motifs within certain genres, particularly the sub-types that fall under the umbrella of speculative fiction, are very popular, not only to uphold the whimsy of their respective genres but to add cohesion to the narrative by crafting characters that become an extension of the story's theme itself. This is a useful device if you're writing an allegory or parable, but it can toe the line of absurdism too much, destroying the realism that an author might have been aiming for. And if you're targeting a specific reader demographic and genre that don't favor the absurd, it will backfire. So you have to understand your audience's expectations.
But each serves their own purpose and aren't mutually exclusive. Again referring to JK Rowling, her Harry Potter series incorporated both philosophies for entirely different reasons. She used absurd names to denote foreign origins, to symbolize and to stereotype, to invoke wonder and satirize. But she also used realistic names to ground the reader and enable them to suspend their disbelief when confronted with the ridiculous.
Harry, for instance, is a very ordinary name meant to help a reader relate to the character because this character serves as a reader surrogate. The reader can more easily insert themselves in Harry's shoes if they relate to his status as an ordinary person freshly introduced to the world of magic, because each reader is, after all, a non-magical muggle from ordinary origins themselves. Whereas other names, like Narcissa Malfoy, are obvious aptronyms meant to stereotype and symbolize her personality as a narcissistic maladaptive person... which is also a foreshadowing device since this character is a villain in the story.
So the importance depends on how the author intends to present their ideas.
If I read about a character and the name is revealed, I expect that the name matches the setting and the names in the world in general.
In a medieval setting of Europe, I would expect that no one is called "Chantalle" or "Kevin", because those are names that got popular later.
Names have a certain ring to them and help to improve the impact of the story. 1001 Nights wouldn't be the same if a Joanne told the stories. No, Scheherazade has a more familiar ring to it and matches the setting perfectly. So I think the naming is pretty much a mix out of both: thematic and realistic origins. A name can have many meanings. So the mix makes the cake.
Keep in mind that "realistic" is not the same as "statistically probable". Smith, Brown and Jones may the most common surnames, but in all likelihood most people you know have other surnames. Same with popular first names: yes, you've probably met a lot of people that share the same popular first name, but you've also met a lot of people with different names, and how many of those made you go, "Wait, isn't that name kinda unrealistic?"
Common names are realistic, but so are uncommon ones. In fact, a story peopled with just Smiths and Browns and Joneses would strike me as more unrealistic than one featuring none of those names. (Unless for some reason, this was a feature of the fictional world, of course.)
As with everything, you need to find a balance. I wrote a random name generator once for a game that created a random cast of characters each session. I spent quite some time tweaking the probabilities, and I found that the character names felt "most realistic" when the character set featured both names that are very common and names that are decidely less so.
Also, while rather rare, there are people whose names strangely match their personality, profession or, why not, clothing habit. That, too, is realistic. Sometimes, this is coincidence. At other times, a person's choices may be subtly influenced by their name and how their environment reacts to their name. In your example, you could have your character prefer to wear black clothes because he's proud of his heritage.
As long as the meaning is not "in your face", I don't see anything wrong with having characters with meaningful names.
For example, in Harry Potter, both Albus Dumbledore and Sirius Black have names that evoke colours, but neither struck me as odd: Albus because I didn't even realize it meant "white" until much later (when it was just a nifty bonus) and Black because it seemed a common enough name (and the "black equals evil" expectation is subverted).
On the other hand, Remus Lupin may be a bit too much. I didn't notice when I first read the books, but I guess for more savvy readers, a meaningful name could end up spoiling a twist. Also, in hindsight, I wonder how his parents ended up choosing specifically that name. Fate?
You do not need to sacrifice realistic names to have thematic names. Just like in real life characters can come to be known by different parts of the name, and that makes all the difference.
Think about a character named Dick, now think about Richard. Or perhaps we can have Mr Nixon. Or if all else fails we can call him Tricky D.
Even if you mention the character's full name at some point, the reader will remember the name you use over and over, and that is the feeling that they will get about him or her. Even further it is an easy way to convey how characters feel about other characters if they use different parts of names.A big upper manager parades around as Montgomery until he runs into the CEO who insists on calling him Monty
There are many factors that would affect what names would work better for your characters.
First, is the character using a name, nickname or pseudonym? A nickname would be given for some reason, a pseudonym would be chosen with some thought in mind. It therefore makes sense for nicknames and pseudonyms to reflect some trait of the person using them.
Second, who gives a name, and when? In some cultures, a person receives a new name when becoming an adult, or when joining a particular profession (for example - Geisha). This trope is also quite common in fiction. Tolkien's elves, for example, acquired names in the course of their lifetime, given by people close to them, based on traits.
A name given as we're used to in Western society, by the parents, could be thematic in a different way - it could reflect what kind of background the child comes from. Take for example Michael Carpenter, a religious character from the Dresden Files series. His children are named Molly (that's short for Mary: source), Daniel, Matthew, Alicia, Amanda, Hope. See a trend here? So, for a minor character, a name would provide information on the character's background.
Finally, when you pick a realistic name, you have a long list of names to chose from. There's no reason why you shouldn't pick something thematically appropriate. Take Michael Carpenter, mentioned above. It's not a name that stands out in a crowd, is it? But what if I told you the guy is a Knight of the Cross? Suddenly both his surname and given name become thematically appropriate, don't they? (And you don't even need to know what exactly a Knight of the Cross is.)
In some settings, you can ignore realism entirely in favour of thematic names. This works best in humorous works, not meant to be taken seriously, or in works for children (think of Cruella De Vil).
However, some readers (me) might find names that are too thematically in-your-face detracting from the story you are trying to tell. The main character in "Good Omens" being called Adam - that's a stroke of genius, tying together the themes of the book. Remus Lupin in "Harry Potter", on the other hand screams to me "my parents knew I was going to become a werewolf, so they gave me both a name and a family name that would fit."
