Hi Stefany -
Interesting that you should ask about yellows. My two cents on the subject as an amateur fashionista is that several factors are involved in the apparent tendency of Westerners to not favor yellows, particularly the earthy yellows. One, in the West people tend very much to like the so-called jewel tones - cool colors like blue, green, black, white, blue-reds, purples, silver - and also tend to prefer glossy and glittery jewelry over matte finishes. If you look at the major fashion house collections, about 75-80% of the time, they are based on cool colors, not warm ones. Cool colors are generally considered more "classic".

Just the opposite appears to be the case in the less developed world - earth tones are favored (although jewel tones are widespread as well) and shiny beads do not get as much attention as the matte ones.

Also, lighter colors like yellow, and white, look more dramatic on dark skin than on white skin. I have found for example that it's hard to wear necklaces of predominately white trade beads. They do not look good up against my skin, which has a yellow undertone. However the mustard yellow beads look fine so I have a good number of necklaces of yellow trade beads. But it seems that the darker yellows all look much better than the pale yellows - and I think this is just a mater of contrast. Anytime beads (or clothing for that matter) get too close to one's skin color, the colors tend to "fight" and do not look good.