Magento 1.9.1 comes with built-in support of Color Swatches.
Swatches provide an alternate way to display the selection of options for configurable products. Rather than choosing an option from a drop-down list, customers can make their selection by clicking a swatch. Configurable swatches can be used on the product page, product list, and in layered navigation.
Check Magento Documentation for complete Swatches Guide