Add a background color to a cell depending on what you write

Who can help me?

I want to add a background color to a cell depending on what I write.
Ex:

If I write "A", "B" or "C" the background color to be BLUE
and if I write "D" or "E" the background color to be RED


Thanks.

I solve the problem

for those interested:
With Conditional Formatting on the cell A1

Condition 1
Formula is =OR(A1="A";A1="B";A1="C")
and put Blue color in format

Condition 2
Formula is =OR(A1="D";A1="E")
and put Red color in format

If anyone knows another way?
Maybe in 1 condition not 2.