Answer
See below.
Work Step by Step
If we want to choose $k$ elements out of $n$ disregarding the order, not allowing repetition, we can do this in $_{n}C_k=\frac{n!}{(n-k)!k!}$ ways.
The order doesn't matter here in the set of candies, thus we have to use combinations. There are $21$ colors for $6$ spots, thus $_{21}C_{6}=\frac{21!}{(21-6)!6!}=54264$