How do I change the color of gkBg

I would like to change the background color of the header (probably gkBg). I tried to change the style 1 - background-color: # ABD8E3 to another color, but there is no change. What to do?
(J 2.5)

best regards,

Maciej

Could you show me your site URL ? It is always easier to check CSS/HTML code on live site because I don't know which color style you use.

At this moment project is on the local computer. I'm working on the original template file system. I want to change the background color on the top of the area in which are located the menu, logo, etc. As for the whole area from the left to the right side of the page.
Thank you in advance for your help.
Maciej

The background color should be in #gkBg selector - of course if you don't make any custom changes in template code.