pnm,
In your Admin area, go to the "Edit Templates" section. In the main file list, find skin1.css and click on it to edit it. Look for the class
.VertMenuTitle. This class sets the "Background-Color" (the color of the box) and "Color" (the color of the font for the title). Both of these can be changed to whatever you want.
The colors are in hexadecimal format (a 6-character alphanumeric made up of letters A-F and numbers 0-9, with the "#" in front). If you're not familiar with this, go here
http://www.lynda.com/hex.asp#, and click on one of the links for the web colors organized by hue or value. Then just replace the original color code in the skin1.css file with the hex code for the color you want. The colors listed at this site are the 216 web-safe colors. You're better off sticking with these, but you can probably do a Google search on hexadecimal color codes to find a full palette of colors with their hex codes.
Also, you can change any colors in the skin1.css file to get the look you want for your store front. You can also change fonts, font sizes, etc. You can do the same with the skin1_printable.css and skin1_admin.css files in the same directory with skin1.css. If you use the Fast Lane Checkout module, it has a separate skin1.css file within its directory (modules/Fast_Lane_Checkout).
Oh, and something I just discovered... when you submit your order through your store, it goes to a page stating "Your order is being processed..." This page has the default orange color scheme. There is a template in the template directory "customer/main" called "payment_wait.tpl". It has its own styles within it so they override the .css files. If you don't like the color scheme, just edit the payment_wait.tpl file to your liking.
You can also ftp the .css files to your PC if you have a web-authoring program you prefer to use. They are located in the <x-cart dir>/skin1/ directory. The folder names within that directory correspond to the folder names you see in the Admin Edit Templates area. Just download the files, change them, and upload them back to the same place.
I hope that helps you. Good luck.
Jill
