Help in choosing correct power supply for LED matrix
Before building a matrix of LEDs I highly recommend you to build a circuit to drive one single led, then a circuit to drive leds in series, finally a circuit to drive leds in parallel. That way you will know how it works, it will help you a lot because it is an elementary subject in electronics.

Answering your questions.


It's possible with only one power supply.
46.5v would be excessive, you're calculating it wrong. If all the rows of leds are going to be in parallel, just calculate the voltage of the row that needs more voltage, in this case the row with the white leds.
No need of two power supplies or two calculations.


Good luck!