Thank you Marko!

For this specific bulb model, you can read the current value by listening for notifications on characteristic ffe4 in service ffe0, and then writing the bytes EF 01 77 to characteristic ffe9 in service ffe5. The RGB values will be in bytes 6, 7 and 8 of the response (these indices are zero-based).

Here is some sample code that does this, and the relevant part in the description of the bulb protocol.

What are you building?