I have long pondered how to get color into my blackwork designs. I like changing line color, and many patterns lend themselves well to this method. But sometimes I want my blackwork design to look like a stained glass window, filled with color, rich colors like you'd see in the greatest cathedrals and churches throughout the world. I'd tried cross stitching to fill, and satin stitch as well, but both overpowered the delicacy of the design and made the pattern look clunky and heavy.
Then I remembered needlepoint. Last summer I enjoyed a little project I gave myself in which I practiced needlepoint stitches I found at the amazing American Needlepoint Guild, Inc. website: http://www.needlepoint.org/Stitch.php
There I learned how to make a Smyrna Cross, an Algerian Eye, and an Upright Cross, along with dozens of other stitches. These lovely specialty stitches are ideal for coloring blackwork. Worked with two threads, I was able to use variations to fill areas and give color to the design. I worked it on even weave. I don't think you could get the same effect with aida cloth. Too many half and one and-a-half stitches, but it's always worth a try. Check out the ANG website. It's a wonderful resource for any stitcher.