If you're looking to add a little color to your application, Shoes has a number of built-in color names that mirror the X11 Color Names used on Linux systems. The method names are all lowercase, and return the color to be used. That means, the X11 color DarkGoldenrod(for example) can be used by calling the darkgoldenrod method and other colors can called similiarly.
In addition to color names, you can also use HTML-style RGB hex values for creating arbitrary colors.
Shoes.app :width => 300, :height => 150 do
:stroke => darkred
title "More colors!",
:stroke => '#efb'