Almost any race of bees can be almost any color variations. Italians can have black bees, and carniolans can be yellow. In general, though, Caucasians are all yellow, Italians are yellow with black stripes, Carniolans and Russians are black. But that is like saying that all Dutch people are pale with blonde hair and blue eyes.
Most of my hives are Italians with a few bees that are darker.
And it is possible that there are bees from different hives mixed in as well.
Caucasians are mostly Gray. Back in the 50's & 60's we had 3 colors of bees: Black were German, Yellow or Gold were Italian, and Gray was Caucasian.
Beekeeper's used to refer to the type of bee as often by color as by name.
Now-a-days we have such a diversity of bee types in this country that we have to widen the descriptiion a bit: Black = German, Yellow = Italian, Gold = Cardovan (aka Italians), Gray = Caucasians, Carnies, and Russians, Rust or Red = Buckfast or Minnesota Hygenics.
With that said most of the bees in this country are mutts being crossed with another strain of bee at some point. What we call purebred is probably only 90-95% pure. As long as it is a bee and comes from one of your hives it's good.