Hmmm there is no "best" site to learn this. You could take a premade code like those shared in tektek.org, apply it to your profile as example then try modify it yourself and see what changed. The keyword is "CSS" aka Cascading Style Sheet. So example you want text color to change, you can google "CSS text color" or background picture by "CSS background picture" .
newbie guide (outdated and some information is false)
http://www.gaiaonline.com/forum/profile-discussion/guide-learn-how-to-code-v2-current-profiles/t.42151201/
the CSS library
http://www.gaiaonline.com/forum/profile-discussion/guide-css-properties-style-sheet-solutions/t.81812403/
Actually this thing is very easy to learn, you just have to read and work your logic around because 90% of the stuffs here is very obvious. Example
#id_about {
color:white;
background-color:blue;
}
the #id_about obviously tells you this code is for customizing the about-me panel
it is also obvious that the code block always started with { and ended with }, the value started with " : " and a property you want to change is ended with a " ; "
now then, there are two things with "Color" keyword. How about if you play it around?? One of them is obviously (again) modifying background color of the about-me section, but about the other one?? try it and see yourself.
Its all about patience and whether you like to give it a try or not. After all, if something goes worng, you can just undo the changes.
PS: Maybe you first time comment when reading this will be like "I dont understand a single word this guy said"... But I know many peeps with no talent and patiently follows after few days (not a week) able to make their own profile
