Funny, I’ve actualy been trying to do the exact same thing this morning, still haven’t figured it out though…
Here are some useful resources I have found (for my specific board).
My board
Based on this image from the add, the 3 small leds seem to be used to indicate if the board is powered and if there is data being transfered on the TX & RX lines respectively.
With regard to RGB LED on the board it seems to be this module (atleast that is the case for me, also if you scroll down on that website and “View More” on the product details part it has pretty detailed specifications).
Also (for my board) it seems it is connected to GPIO47 and NOT GPIO48, so make sure you check the exact specifications of your board.
My board:
I also found some github posts on the getting the led to work but haven’t figured out how to transfer their findings to esphome. (I can see if I can find them again if you’re interested).
I’m goning to keep playing with this to see if I can get it to work, I’ll let you know if I figure it out 