I usually like multiple colors on a ball but if it's too bright then everyone, including (and especially) me, can tell when I miss it at the bottom, grab it, top it, fluff it, etc. A good example is with my Candy Corn Boost.
But I also like solid color dark balls provided the pin is also dark. I can tell by sound and generally by results if it's picking up in the right spot, so I don't need to see the pin (more on that below).
There are really only two kinds of color problems for my tastes:
1) Really bright single colored balls (e.g. Forza Redline, Beyond Ridiculous, Venom Panic, all gold balls). Blech.
2) Dark colored balls with a white pin. I notice that lots of balls poured in Hopkinsville are dark but with white or yellow pins and no logos to the right, so in essence all that I see rotating on the ball is the pin. I HATE THAT. Examples are my Encounter, 920A and 920T, Salute, etc.