Tails group

I joined it but my user name isn't yellow or anything how come? Yes the leader did let me in.

Because you are a moderator. If you weren't one, the color would show.
On the main index the order of the usergroups/staff also suggests the order in which colors show on your username. Because Moderators are the second in line, after admins, all fan clubs, and other usergroups, won't show the designated color, because the moderator color is of higher order.
It's the reason my names not red or purple while I'm the leader of the Knuckles Group and Media Group respectively.

I wouldn't know that ok can half my name be the color of mod and half the other?

Shiny Star wrote:

I wouldn't know that ok can half my name be the color of mod and half the other?

No, since you're a moderator, you have to be that color and your name will never be two colors at the same time. You can only have one color.