Some of the current answers are part of the problem that you have: they provide a cognitive approach.
When your writing lacks "color" it lacks emotion. You cannot analyse other texts and consciously construct your own writing based on the results of that analysis to contain emotion. You cannot follow certain rules to create emotion. The result would be fake emotions.
Colorful, that is, emotional writing comes from the authors feeling something about what they write about. Colorful writers remember how they felt in similar situations or simply imagine how they would feel in place of the protagonist.
Writing is like speaking in this respect. If someone tells something that he does not care about, his voice will be flat and emotionless. If someone tells something that excited him, that is, something that made him angry, afraid, or happy, then his voice – and his choice of words – will reflect those emotions and his narration will become colorful.
So what you need to do is
You write that it is "the engineer in you" that causes you to write beige text. I think it is not your professional training that influences your writing but rather that you have chosen your profession to fit your personality. Maybe you belong to that half of the population that does not emote so strongly.
If that is so, then attempting to write more colorful may turn out to become impossible to achieve for you, because you simply don't work that way. You believe that you must write colorful prose, but you really don't have to. There are good and successful writers, like for example Stanisław Lem, who have built a career on writing intellectual, even-minded fiction.
So instead of trying to write more colorful – which just might not be for you (but I don't know and you might have to try to find out) – you could instead
make that "engineer" perception your trademark and evolve it.