Changing Colors Menu

Hello, i use these Theme with the color blue. But, i want to change the color in another blue. Only for the Menu, for the rest, the link-color at the themeoptions are enough. I tried with childtheme - but no chance to change. Perhaps the problem ist the blue.css with the color-folder. Usually i can change colors at the style.css from the parent theme. And I still noticed something. when I move the mouse over the "no comments", the font is unreadable because the color is the same as the font color. I hope I have made myself clear. Can you help? Short Note: I am a beginner and not a professional programmer in terms css. Thx.