Web call to turn lights on doesn't catch color on first call

So I’m sure this is just something I’ve screwed up, but here goes; I’m using web calls to turn my LED strip various colors. I have specific calls set up for various colors.

For all of them, the url is https://myurl/api/services/light/turn_on?api_password=mypass

The content body for blue lights, for example, is {"rgb_color":[8,48,192], "entity_id":"light.flux_window"}

When I first make the call, all it does is turn the lights on; they keep whatever color they had previously. If I make it a second time, they go to the correct color.

Does anyone have any suggestions for this?

Is it working if use the HA web interface?