I have a automotive theme which i buy from themeforest. I installed it, but now i want to setup the the header that it can hidden when i scroll down and show when i scroll up. How can i do that.
The best way to get this answer is Contact your purchased Theme Author.
Otherwise you have to make it by customizing your theme. About the change bg color you can set a background for the white area parent div as like:
selector {
background-color: color-code-of-body-color;
}