I think with 300 color names, you would want to group them, as many users may have different ideas as to what the different names of green or blue are to achieve the same result.
I’ve never searched for rgb/hex in a photo - but I may just not be the right audience for that feature. Listing the dominant color swatches in the info panel would be interesting though and a nicety, as long as it didn’t contribute to clutter with other features. I could envision selecting a photo, then clicking on one of the swatches to find other photos with that as the dominant color, as opposed to manually trying to figure out the color code/hex/rgb. Random idea for