You could try with a RESTful Switch for basic on/off.
Are you able to change they way your LED works to work with MQTT instead? Then you could use MQTT JSON Light… That’s what I did for my LED strip so I get full access to the colours and more effects…
Another way / if you can’t change the LED controller, you could create a few shell commands for on/off and hexvalue (pass the value as a parameter) and a few https://home-assistant.io/components/sensor.rest/. Finally create some inpuit_boolean for on/off and either 3 input_number for your R G B values or an input_text for your hex value. Add a few automations that trigger on change of these inputs.
Not sure how you can get the colour picker without the “right” light component to be honest. This is now a bit it of my area of “expertise” (if there was one)