When you click the 'Mass Downlaod' tab for the Dirt55 Paint Schemes that are
Here it opens a new window. If you are after all of the schemes, and
if all of the files names are gray, then you only need to click the 'Submit' button. If you want to 'pick and choose'...select one and then, while holding down the 'Ctrl' key on your keyboard, select the other ones you want one at a time.
Mind you, I've never done this myself personally but that is how I believe it would work.
edit: OK...I just tried it for the sake of discussion and I received an Avea Media notification stating, 'The script is taking a short break to avoid server overload. 59 of 64 done' so you may have to download them all in stages.