Brush Color Problem

I have just downloaded a package of brushes for photo shop and converted them for gimp use. The brushes work, the only problem is that I can not change there color like preset brushes. I don't know if this helps but these are the brushes that I used: http://www.bittbox.com/freebies/free-hi-res-splatter-photoshop-brushes

and I followed this method to convert and install them: http://www.youtube.com/watch?v=UrBaNis4Z20

Does anyone know what I can do. Any help would be appreciated.