Here's my best approximation of the current FlexJet paint scheme for the Hot Start Challenger 650. FlexJet flew Challenger 605s in this paint scheme in the late 2010s, but has since resold those aircraft.
The FlexJet livery uses an iridescent paint that appears as different colors in different lighting and angles (see FlexJet photo below). For now, I've created a livery for the red color. Informed suggestions on how to emulate this iridescent paint in a texture file are welcome, my attempts at custom NMLs did not achieve the right effect.