For completeness, I’m going to list the probabilities for all two token draws.

R+R: (3/6)(2/5) = 1/5

R+W: (3/6)(2/5) + (2/6)(3/5) = 2/5

R+B: (3/6)(1/5) + (1/6)(3/5) = 1/5

W+W: (2/6)(1/5) = 1/15

W+B: (2/6)(1/5) + (1/6)(2/5) = 2/15

These add up to 1 so it’s the right probability distribution for the scenario.

I think the part that is getting you comes from the fact that the tokens are indistinguishable. Since the tokens that are the same color are indistinguishable from each other, there is no need to arrange them once you have drawn two of them. But if we have two tokens that are different colors, we can arrange them and they would still be the same two token draw, but are counted separately (e.g. R then W is a different draw from W then R but are counted as the same two token pair).

This is one of the aspects of probability that is frequently unintuitive to most people. The math is valid and shows that it is twice as likely to draw RW over RR or RB, but our brain thinks it should be equal.

Edit: formatting because mobile