Warhammer 40,000 – Jockero Orange is my friend. This nifty color has been the basis for a very large (an ever growing) commission army for one of my favorite clients. Granted it's not flashy or super detailed but working on this job has truly expanded my ability to quickly assemble, base and paint a large number of models in a short amount of time. This force really represents the most economical way to get a great looking army on the tabletop.
My client also did what I consider the smartest way to collect Space Marines. Create your own chapter with your own color scheme and icon. That way everything you have looks great together and you can change up your army to fit whatever codex you want to play. It saves you from having to redo basic troops and transports anytime you want to change tactics.
The latest batch of models I'm painting up are 3+ Colors, with a wash, custom decal and basic basing. He's given me almost every special character, some whirlwinds and an allied tank force that he wants to all match up. I reminds me a bit of the Tyrants Legion idea one of my other clients had, keeping everything consistent opens the doors to lots of options.