Setting RGB LED values on boot

I have my custom built 3d printer working quite nicely now with Marlin and RAMPS, and the RGB LED support is great since getting it working with help on this forum. What I would like to do is have the LEDs start fully on white. I have seen that I can load custom boot up gcode using an SD card, but I don't have access to the SD slot and it is disabled in my firmware build. Is there another way to add either custom gcode or set the three pins to 255 as it boots? I assume that there will be a function that is called that sets pins to the expected states and perhaps I can add the commands in there, but I am not entirely sure what I am looking for. Does anyone have any tips, please?

can't try it at the moment, but give this a try

in Marlin_main.c line 12708 (in my version) is the following

  #if ENABLED(RGB_LED) || ENABLED(RGBW_LED)
    SET_OUTPUT(RGB_LED_R_PIN);
    SET_OUTPUT(RGB_LED_G_PIN);
    SET_OUTPUT(RGB_LED_B_PIN);
    #if ENABLED(RGBW_LED)
      SET_OUTPUT(RGB_LED_W_PIN);
    #endif
  #endif

change to

  #if ENABLED(RGB_LED) || ENABLED(RGBW_LED)
    SET_OUTPUT(RGB_LED_R_PIN);
    OUT_WRITE(RGB_LED_R_PIN, HIGH); // turn it on
    SET_OUTPUT(RGB_LED_G_PIN);
    OUT_WRITE(RGB_LED_G_PIN, HIGH); // turn it on
    SET_OUTPUT(RGB_LED_B_PIN);
    OUT_WRITE(RGB_LED_B_PIN, HIGH); // turn it on
    #if ENABLED(RGBW_LED)
      SET_OUTPUT(RGB_LED_W_PIN);
      OUT_WRITE(RGB_LED_R_PIN, LOW); // turn it off
      OUT_WRITE(RGB_LED_G_PIN, LOW); // turn it off
      OUT_WRITE(RGB_LED_B_PIN, LOW); // turn it off
      OUT_WRITE(RGB_LED_W_PIN, HIGH); // turn it on
    #endif
  #endif

Edited 2 time(s). Last edit at 06/05/2017 09:31AM by Dust.

Cheers, will give it a try in the morning as I am just off to work.

Compiled and uploaded this morning and it does exactly as intended. Thanks ever so much