Just an idea, dunno if it would work...
current always flows the path of least resistance. so...
you want to find a way of making the blue LED's having a higher resistance than your red one.
The red would then be on an RPM specified switch. But the red LED circuit should have an over all lower resistance than the blue set.
the current then would find it easier to go through the red LED by bypassing the blue ones.
When the switch turns off. (rpm activated again) it has no choice but to go through the blue....
If anythink it would make the blue very dim but LED's do not light up if they dont have the correct current i believe?...
does that sound like it could work or am i talking bullpoo??