Date and coloring cells

[madd_mike]

I have three fields in a database, dateofevent (yyyy-mm-dd), artist & venue (both text). I get the output okay but I want to seperate every other date with a light green color. So if my DD ends even (2,4,6,...30), the cells are light green and if the date is odd (1,3,5...31) leave them alone. I just don't know how to do it. I tried modulus (dateofevent % 2) but every cell is white. Can anyone help me?

[bastien]

$c1="lightgreen";
$c2="white";
$color = $c1;

($color == $c1)? $color=$c2 : $color=$c1;