Hi Brian

Take a look at this code. ButtonCount starts with 0 and then loops between 1 and 3 depending on your button presses. You may want it to roll over to 0 and have an all off program too. EDIT : My post assumes you are using a high input as indication of switch being pressed.

Code:
Red var GPIO.0 
Green var GPIO.1 
Blue var GPIO.2 
SwitchPin var GPIO.3  
ButtonCount VAR BYTE 

    ButtonCount = 0  ;Make sure LEDs are off 

    HIGH Red  
    HIGH Green 
    HIGH Blue  

MAIN: 
SWITCHLOOP:
    if SwitchPin = 1 then
      ButtonCount = ButtonCount+1
      if ButtonCount > 3 then ButtonCount = 1
      while SwitchPin = 1: wend     ' wait here while the switch remains pressed
    endif

    If ButtonCount = 1 THEN GOSUB RedProgram 
    If ButtonCount = 2 THEN GOSUB GreenProgram 
    If ButtonCount = 3 THEN GOSUB BlueProgram 
GOTO SWITCHLOOP 

END  

RedProgram: 
    PWM Red,127,100 
RETURN  

GreenProgram: 
    PWM Green,127,100 
RETURN  

BlueProgram: 
    PWM Blue,127,100 
RETURN

END