Go to the groupfooter format section rigth click choose format then color and try this.
if RecordNumber mod 2>0 then crYellow else crNoColor
or if you want to creat your own color then try this.
if RecordNumber mod 2>0 then Color (200,242,253)else crNoColor
200 is red, 242 is green,253 is blue this gives you a ligth blue.
You will find this fuction in x-2 function under color constants.
This works for me.
Dave