Comparisons and Superlatives of Colours

English-Russian Translator has got the right concept.

However, I would even shorten the list to only white; everything seems to me to be either literary "acceptability" or words that have arguably been gradually accepted over time.

I know for sure 'white', 'whiter', and 'whitest' work. Instead of blacker, I would use 'darker', although I know it's not exactly the same.

Superlatives (like best) and the other term for which I forgot the word (like better) are not limited to having -er and -est suffixes, you must remember.
For many of the words, I would use more and most instead. Like fast would turn into faster, just as strong would turn into stronger, but not all words are like that. Like, 'he is most brilliant at the logistics of..' or 'he is more brilliant at the logistcs of..'. You can't really use 'brillianter'.

But, as mentioned, some words are eventually being accepted like bluer or bluest (I personally still would not use that). 'Tan' would work when you're actually talking about a tan.. but since it's been used that way, it doesn't make a difference whether you're talking about the colour.

Gray/grey can definitely be used, as when someone is talking about the greying of one's hair.

Btw, I thought red, blue, and yellow were the primary colours.
In any case, the general answer I would give is depending on who you are you will argue differently. Like, one who is used to redder being an actual word would say more red or most red doesn't make sense. And, people who don't use it, would say the proper way is more red or most red. I sometimes the -ish suffix when I don't know. Like 'this sun is much more yellowish than it had been before..'

As for silver and gold, I'd assume silvery (for -er) and most silvery (for -est) would suffice? Not sure about that second one though. Same thing for golden and most golden.

Based on red,thecomparative superlative is more redish and most redish, reder and redest is not acceptable in the rules that guides english language