PHP functions – Admin menu to select style sheet

I’m developing an options page within the WordPress Admin. I’ve managed to implement a custom banner and custom logo option.

I’d like to have a function select a stylesheet depending on an option within my admin menu:

I have the following function:

<?php echo $options['color_scheme']; ?>

…which returns an item from the array ‘Red’, ‘Blue’, ‘Green’ or ‘Default’.

Clearly I can change these colors to the url of a stylesheet, but I want the drop down menu within my admin page still to show just the colour names.

How would I go about this?

Please let me know if I made no sense! Thanks in advance.