Background Colours in Nested Replies

Three things first: I *love* the Atahualpa theme and am enjoying its amazing array of customization options (so thanks!). But I'm no coder and my PHP skills are exceedingly weak. As are my CSS skills.

My problem is this: I've altered the default colour scheme quite radically and when I turn on WordPress threaded/nested comments, the text and background colour of the replies is not just ugly but completely illegible. I'd like to change them so that odd- and even-numbered comments appear with alternating backgrounds, as I have already done, but ALSO so that the nested replies do not appear with different text and background colours -- the only different trait they should possess is increasing indents.

Where should I be looking to make these changes? (Many thanks in advance)

Ooops, looks like a little research into style.css.php can do wonders. Problem solved (background: transparent) and I'm back on track. Apologies for the diversion!