This is the information sent by the GL.iNet support specifically for the GL-MT300N-V2 cd3 model,
"Hi
Sorry to inform you that the led color is unable to change, but you can modify the middle light.
The led lights on new device seems to be changed to white light, which are unable to change to other color.
Sorry for the inconvenience this caused you.
Regards,"
My solution:
Disassemble and paint inside the desired colors the power indicator (red) and the wifi indicator (blue). They are two transparent bastocytes.
Too easy.
Regards.