How can I create an emacs color theme so that it changes background of the line when it has some keywords

Question

I want to create an custom theme so that emacs changes the background/foreground color of the line of text when that line has some keyword?

I see this tip http://emacs-fu.blogspot.ca/2010/04/creating-custom-modes-easy-way-with.html

but it only changes the color of the keyword. I want to change the whole line color when it has the keyword.

Thank you.