I'm sure it's working correctly. It's just I have a certain part of my creature that I want painted a certain color.

I created a Lombax, from the Ratchet & Clank franchise, and it looks almost spot on. Except for the nose. Lombaxes have black or brown noses like this:


And my creation looks like this:


Is it possible to change the color of his nose alone, or do I gotta make due with what I have?

You'll just have to do with the already existing patterns, since customization of where exactly you want the paint isnt possible.

There's one way to use parts to make strips and such, but that can be quite complicated. But I have one tip that you may have use of in this case, among the detail parts there is one certain part that looks like a bunny tail (that fluffy round thing )
It always takes the color in the second layer, so if you choose for example pink the entire "bunny tail" part will be pink. Since you can flatten this part out, you can place several of them to make something that looks like stripes!

Hope I my advices was helpfull, and feel free to comment if there's something else you wonder