The wiki says there's just 4 colours - blue, green, red, black.
I propose to add all the rest - white, yellow, orange, purple, pink, grey, brown and so on. Lots of colors.
Give them a variety of origins, so you can't just get your hands on all of them. Orange is from a plant only elves can grow, yellow is from a tropical plant, purple is from a tropical sea slug that can be fished on tropical coasts, pink is another elven plant, and so on.
So that you will need to trade and go on the lookout for the dyes if you want them.
Secondly, improve the interface for the clothiers shop, so that after choosing material you can choose colors. For instance -
"Make silk hood" becomes (in the case the player has dyed some cloth blue and yellow)
Make any color silk hood
Make uncolored silk hood
Make blue silk hood
Make yellow silk hood
This makes it possible to customize the color palette of your dwarves. You can like give them blue clothes with a yellow hood and cape or green above the was and red below. You can make them look like your favorite sports team or just roleplay them looking in a certain way.
(The shop change on it's own would make it possible to customize the look. You could choose to spare the blue dye from dimple cups for cloaks and then you can get a fort of blue cloads if you like that.)
In theory it could also be used to make it visible what sort of dwarf you're looking at. If it some day becomes possible to choose who wears what, you could have yellow hoods for nobles, red hoods for soldiers, blue hoods for valuable workers and white hoods for peasants and cheesemakers, or whatever the player wants. I'd find that nead and practical myself.