Many popular Bluetooth light bulbs use the same underlying "Triones" protocol. For example, this one is available from Ali Express. Weirdly, a lot of the Bluetooth smart light bulbs from Ali Express are in fact the exact same bulb (I know this becuase I've now got a drawer full of them from different sellers and they are identical right down to the packaging). Look for bulbs that use the "HappyLighting" app; they seem to often be Triones compatible.
There are three tabs for Triones devices: color, demo modes, and white.
The Color tab lets you set the exact color of the bulb using a color picker. You can
point to the color you want or you can type in the red, green, and blue values directly.
Only some Triones-compatible bulbs will do the demo modes, and unfortunately there doesn't seem
to be any way to tell which bulbs support it and which do not.
The white tab is used when you just want pure white light. That tab also includes a power
switch to turn the bulb on and off. When a bulb is off, just setting the color won't
turn it on; you have to also press the power switch.