Plenty. I can do it, to a certain degree of accuracy. At least enough of a degree that there won't be a more accurate english word for the color in my vocabulary.
It helps to remember that:
1. #RRGGBB
2. B + G = Cyan
3. R + B = Magenta
4. R + G = Yellow
5. Equal amounts of all three channels = Gray
6. #000000 = Black
7. #FFFFFF = White
Think of the rgb color space as a cube, with each of Black, White, Red, Green, Blue, Cyan, Magenta, Yellow on the vertices. Then you define any hex color as point somewhere in this cube and it's pretty easy to imagine what it'll look like.
In my 20's I've done a lot of web design for about 5 years. After 2, maybe 3, years I could "see" the colors and their nuances in the hex codes. More interesting was the reverse lookup, seeing a color and visualizing the hex for it. Fun times. Not sure I still can do it...besides the most obvious ones. But then I was not bad, about 90-95% accuracy ( measured on the deviation of the light/color wavelength ).
