A Question about colour schemes

Hello, I want to have a number of different colour schemes for my users, which will all be defined in spereate css files (unless someone suggests a better way of doing it), and say my files are schemes/default.css, schemes/blue.css, schemes/red.css etc, how can I set it so that on the front page in a user panel for example there is a drop down menu with the colour schemes, and also one in the profile, I want it so that when they select it, the next time they come back it stays on that colour scheme for them, would the best way of doing this being with cookies or maybe like an entry in the mysql user database?