Well, Red Bull certainly had no issues coming up with special 'one off' liveries in previous years - which probably shows it's not as commercially impossible as you'd believe to come up with something a bit different. You only have to look at the buzz that those created to see the effect that unveiling something like that has.
It's funny you mention Formula E too - a series where most of the current grid is using a combination of black, red and white. Yey for originality!
And on a sort-of related note, the Red Bull Holden team in the Australian Supercars series manages to make their livery different every year, even though they've got the same sponsors. Wonder how they manage that?
Nobody complaining about being unable to recognize the team? Thankfully not it seems. The last we need is any motorsport governing body mandating even stricter regulations on livery design.