Check arg length for response

[jetpax]

Fix response was not correctly generated, and add check for correct arg length

[dyarkovoy]

Can you also move the

uint32_t led_color[3] = { 16, 0, 16 };  // Red, Green, Blue  (0-255) 

from the global scope into the Rmtled class?

Consider the case where we have 2 or more instances of Rmtled on different pins, they will share the same global led_color, which is probably not what we want.

[jetpax]

Indeed, done.