Lots of "easy" ways to do this in PS, the easiest for you might be to recolor the originals that came with your forum though.
Open the gradient in PS, click
Image in top toolbar, choose Mode > RGB color. Now open layers palete and copy the layer/image by dragging down to the
create new layer icon. Untick it from showing then click on the copied image above it. Now click on
Image again on top toolbar, then select Adjustments > Hue and Saturation and slide things around to get the color you want to use.
Or, just make a new image same size as the original gradient and fill it with the gradient tool.
That should get you going.