I gave away a lot of art supplies before moving to Texas, but I still have some whole and half sized pans that hold colors I no longer use. I don't want to get rid of the little pans, yet I don't want to just throw the old paints away because they are artist-quality (as in, more expensive).
I used to have around 30 watercolor paints in my large studio set. Then cut that down to maybe 24. Now, I am down to the above 18. Among these are several convenience colors that can easily be mixed, but sometimes I just like to "grab and go". A couple of these (like blue apatite) may eventually go as well, but I'll keep it until the tube is empty.
On the left side above are the limited palettes I normally use, one for color and one for just a bit of shade or light in an ink drawing. I had three Altoids chewing gum tins (no longer available), so I put together three more limited palette sets, on the above right. One on the bright side, one of muted color, and one with Liz Steel's limited choices just for fun. (She doesn't have the mixed gray in hers but there was an empty space and I learned of mixing my own gray from her.)
Recently Irish artist Roisin Cure posted the colors in her paintbox --- many I don't use but I had similar colors in leftover full pans so I put together a "Roisin" set just to play. I love her use of indigo for black and shadows; I don't have indigo but I do have some leftover Lunar Blue that might work. I wondered about her not including a burnt sienna-type color, but found I could mix one. Not liking pink, I don't have 'opera pink' but do have a quinacridone violet that was once sent to me by mistake. (The seller told me to keep it at no charge.)
And that ends this particular sketchbook, a cheap ($4) journal found at Hobby Lobby. This last 2-page spread was used to test inks and color mixes while working elsewhere in the book.