You can do “All lights” or a specific light. You’d need the rule for both of your lights if you have more than those two and didn’t want all lights to loop.
You can use the same ifttt trigger for multiple recipes. It’s a little awkward to set up, but it works fine.
Say you have three lamps in the living room, Lamp A, Lamp B, and lamp C. They are of two different brands. But both brands have an IFTTT channel which allows a color loop.
If so, you can set up three IFTTT recipes:
-If switch X turns on, Then Color Loop Lamp A
-If switch X turns on, Then Color Loop Lamp B
-If switch X turns on, Then Color Loop Lamp C
Then just use “Alexa, turn on X” and all three lamps will do a color loop.