Limit an array based on criteria (percentile if another variable returns true)

I'm trying to calculate a percentile, limited by a second variable.

i.e., I want to return the 0.8 percentile value for B:B, but only calculated among those values for which A=red.

A..........B
red.......5
red.......6
red.......4
red.......5
blue.....8
blue.....9
blue.....7
blue.....8
blue.....9


I imagine that there is a common way to apply a criteria to the array that's defined in the PERCENTILE function - but I could really use to be pointed in the right direction!

Thanks in advance!

Try an "array formula" like this

=PERCENTILE(IF(A2:A10="red",B2:B10),0.8)

confirmed with CTRL+SHIFT+ENTER