For highlights I usually shift my hue towards yellow and up the saturation, and for darker shades I shift it towards darker purple/blue's and lower the saturation, depending on the "base color". It's mostly eye-balled, I have grown more pleased with high contrast from shade (often black) to highlight.
This is just absurdly awesome. Just how many million years did you spend to perfect your craft like so!? If i could fave something more than once, this would be one of the things i'd never get done fave'ing. WELL DONE.
SO. MUCH. AWESOME. Jet versus dragon? Strangely reminds me of the books I'm writing... Spending as much time as you must have spent to create this pixel by pixel is something I doubt I will ever have the patience to do. You did a freakin' amazing job! I salute you, sir!
... Am I the only one here rooting for the jet...? Sure, the dragon could probably take out the one jet, but not a whole fighter squadron.