I'm sure there is a technical term for this, but I don't know what it is. My question is best illustrated with the button I'm working on. This is how the button should look after I'm done, although I'm going to change the words.
Notice how this gives the "illusion" of being higher-res than it actually is? Using not just white and red, but a variety of shades of red inbetween.
How can I reproduce this effect with PhotoShop. Thanks!