There’s wide latitude for what counts as the five colors of mana. Any shade of red qualifies as red, and so on. Some dark shades of purple can likely pass for black mana, and some light shades of yellow can pass for white. We do those on cards sometimes.

You can add any color of mana in Un- games, though, so if you really want turquoise mana, go for it.

If you’re wearing layers, you can count any garment that other players can see.