Reverse momentary N.O. Switch behavior using PNP Transistor?
You need to omit Rswitch so that the transistor base is pulled completely up to the emitter voltage....that's how you turn off a PNP transistor. 1k for Rbase will give you about 12mA of base current which seems like a reasonable choice. Without knowing anything about your LEDs it's hard to say whether the 150 ohm resistors have the right value. You might think about using two transistors, one for each string. You can just connect both bases to the switch and both emitters to 12V. That will reduce the power dissipated in the each transistor although it's probably not necessary.