Question about line following

i've bought the single line detector
http://www.lynxmotion.com/Product.as...8&CategoryID=8
and the line tracker ,now im experimenting with the single line detector it works fine with black and white .. but the problem is im using it for robocon 07 contest and the background is blue and the line is white , im having some problems for tuning the blue color , is there any solution please

thanks alot

Ahmed , EGYPT