challenge? change color of gif/ jpeg online

Hi,

see http://www.mkbhomepage.nl/posting/ for more explanation.

I want to be able to change the color of an image (1 color only!) based on users input, to ANY color.

I also need to keep my background images visible and transparancy.

I made a page with an example and a clearer description of the issue. See http://www.mkbhomepage.nl/posting/

Who can help? I have only litttle experience with java (copy paste) and need clear instructions/ good reference sites/ tutorials for implementation.... Thanks!!

PS: I read something on pixelgrabber, is that the solution? How?