h1 color

Hello, i would like to modify the h1 color (that is black by default); no problem to do it with css code, but if i insert the color in this way, then the option “White Text in Page Heading” into the page settings doesn’t work.
I would like to have generally a green color for h1 heading, but have the possibility to have it in white when i put an image on his background.
test-grumelliepennati.it

thanks in advance for any solution
Alberto