So, not only do I love exploring the nature of being through fictions about conscious robots, I also taught a robot to see in color as part of my senior project in college, so I'd say this is right up my alley.
So here's the conundrum. If I was playing the lead coder of the color recognition code to the Robot, I would code it to recognize a certain RGB threshold and code it to vocalize that color as a language term for the user interface, so internally, it sees in color codes, but in discussing the matter, it would express the specific color.
If this is a learning robot and I was a clever coder, I might teach it that what it identifies as an RGB encoding is called yellow and over time, it would reinforce the learned nature of the color. With enough repeated correction, it would call something yellow on it's own because it falls within accepted range of defined yellow (Which would be some range with only red and green colors over zero).
But a robot that is self aware, that's a whole other machine. To be fully self aware, a machine would have to have a coded acceptance of it's existence and it's responses... and choose to ignore the code. If it sees something yellow, it's coded to say it is yellow, but it might, for any illogical reason, describe it as RGB or Hexadecimal codes for that shade, because it chose to do so... thus, the robot might identify that for some people it, will be hyper-logical and use the ludicrous precision and in others, it will describe the object as "Smaller than a breadbox" depending on it's situation. It could be the insanely precise answer is annoying to the human companion and the robot knows this and wishes to amuse itself. It could be that society is not ready for a robot that is fully self aware and will affect an "accent" among those who assume it is an ordinary robot, but return to a more vernacular discussion among those in the know because it's as much an individual as they are.
At the end of the day, you too could use RGB codes and Hexidecimal color codes to describe colors. It's insanely not need and Red Green and Blue are much better methods for getting the point across to other humans, but hey, it's your choice, screw what other people say. If you want to say your favorite color is RGB(255, 208, 92), you do you, boo!
After all, describe that color without using any words or likening it to other objects. What does it look like? Hard right? How do I know that if we look at the same red apple, I am looking at the same exact color that we both call red. Maybe red to me looks purple to you? How would we know? This is a phenomena of thought called Qualia, which is an observable quality that we lack the language to describe. I cannot tell you what a color is without defining it by other ranges of the scale. It's got an RGB value. It's got a Hexidecimal value. It's got a CMYK value... and a wavelength... but I cannot describe yellow without likening it to other things. This is a limitation of experience. How do I describe a color to someone who has never seen that color before?
Oh, and fun fact, if your story is dove tailing into a techno-pinochio, describing color is a wonderful discussion piece. The human eye is capable of experiencing a wider range of colors than any computer can encode... so when you robot becomes human, he will notice the world is more colorful, but he couldn't explain why... perhaps he could tell that he's never seen the sky look that blue... but he couldn't adequately communicate the difference to someone who was human from the start.