how to change the two stripes under primary links?

Hi all,

please help.

I have sucessfully adapted the great Aberdeen theme for my page www.ekoblog.cz, but one thing I still cannot find: under the primary links menu are white (#fff) and grey (#d0d0d0) stripes and I cannot get rid of them (see enclosed picture).

I tried to edit li background, but the stripes are independent on this. I also tried to scan styles.css for #fff and #d0d0d0 and chnage, but it also does not work... :-(

Does anybody know where is this thing defined and how to edit/get rid of?

Thank you very much

Cheers

Antonin