Cannot Change style.css Hex Colors Without Losing Theme Images

Hi WP community. I am having a hard time with trying to change the hex colors in the CSS theme (Pristine) I am using. When I edit any of the colors, I lose the top header images (Oh! San Diego and the Cityscape)

I’ve changed the themes images successfully. However, whenever I try to edit the hex colors in style.css the images disappear. I have tried changing them one by one and uploading and even colors that don’t seem to be involved with areas that have graphics cause them to disappear.

Would anyone have any clue as to how I can change the colors in style.css without losing the themes header images? I truly appreciate any suggestions as I have no hair left on my head to pull out ??