Menu Bar – Center, Justify & Recolor

Hello, I am working with Simple Catch theme and have figured out how to center the menu buttons (using this css code that I read from another support thread...Thank you! #header #mainmenu { float: none; text-align: center; } #header #mainmenu ul li { display: inline-block; float: none; }). Where I'm at now is that I would like to stretch the menu buttons so they are all the same size and justified within the overall bar. Additionally I would like to put CSS code in the Custom CSS box to allow me to change the colors (background/font) of the menu, sub menus, etc. I saw a few other strings with recoloring information, but all the code I tried didn't do anything (perhaps b.c I already am using this code above?) Thanks in advance for your help. My test site is www.hipandhealthykid.com