You can
put this solution on YOUR website!There are only three primary colors.
Anyway, assuming there are seven colors with equal probability, the probability that at least one of the other 2499 students is wearing color A is equal to 1 - P(none of them wearing color A). This is equal to
^{2499})
, very close to 1.
If you are looking for the probability that *exactly* one is wearing color A, you have to use the binomial distribution.