background color not matching

Probably due to different monitors displaying colors differently — in which case, no you cannot do anything about it.

It looks like you have the background image for the top section and then a background color below that — which you “matched” to the grey in the image?

If that’s the case, what you might try is creating another background image from the first one of just the plain grey portion — and then putting that in below the first (top) image — and set it to repeat-y. A bit tricky, but MAYBE doable — I’ve done it on static sites but obviously harder with php pages.