Sorry, I know you didn't ask me, but you could use a simple IF and OR argument. Just copy this to the B1 cell

=IF(OR(A1=2,A1=4,A1=6,A1=8,A1=10,A1=11,A1=13,A1=15,A1=17,A1=20,A1=22,A1=24,A1=26,A1=28,A1=29,A1=31,A1=33,A1=35),"B",IF(A1=0,0,"R"))

This is not an elegant way to do it, but it's simple and works. You could also use the vlookup function, but for that you need to create two columns somewhere on your sheet, one containing the numbers 0 to 36, and the the other the colours.