How do some forums get a "gradiant effect" for their category/title bars?

[Velocd]

I have seen some forums, for example this one, use a gradiant color effect in their category/title bars, instead of the default solid color. How does one do this? My guess is their replacing the color attribute with an image source to use instead. If so though, how do you do this?

Thanks

[Velocd]

Never mind actually, I just found the answer to this thread in another post. You can delete this if you want to.