[somebodynew]

It seems conceivable that a red LED based on phosphor excitation could exist somewhere where having the same forward voltage for different colors was essential, but I haven't been able to find one.

Taking into account the different forward voltages for different LED colors is a standard part of designing an LED circuit. One of the LED data sheets I have on hand for some 5 mm LEDs includes a forward voltage chart with 1.9 V for red and 3.2 V for blue.

Do you have a part number for a red LED that operates by illuminating a red phosphor with a blue LED?