Hi Mark,
1- I admit that "De gustibus et coloribus non disputandum". However, may I ask you to seriously re-consider your option of white text on black background? This combination can be quite painful on some eyes (I personally never stay more than a second on web sites offering this kind of combination). On your screen shots, one really hard difficult combination of colors is blue text on black background, the kind of combination that personally I cannot read at all...
2- Developing a theme on Moodle 1.5.x for real use on 1.7 is not a good idea. Indeed there have been a number of significant changes in theme between 1.5.x and 1.6, mainly for accessibility reasons... Which means that when you move your theme developed with 1.5 to your 1.7 site you'll have some unpleasant surprises. May I suggest developing on 1.6 (if you can't have access to your 1.7 site). You can always install any version of Moodle on your own computer, and develop your theme there. That's in my opinion the best way to do things.
Sorry to sound so negative, but you are free to ignore my suggestions, although you might envisage a survey with your target population (students and teachers) to find out whether they can read your proposed color combinations...
All the best,
Joseph
