i assume you have a direct mapping in your mind between squares and colors or actually visualize the board but for those that don't you can convert the column letter to a number then add the two numbers together and depending on whether the number is even or odd the square will be black or white. ie: d1 -> 4 + 1 -> 5 -> white.

there are a bunch of tricks you can do if you use number,number notation but being able to visualize the board is probably better than relying on numeric tricks.