Pick a light, set its intensity and every channel the way you set them in the maker's app, and see the spectrum that comes out, as the maker's own published graph draws it: which colours, how much of each, and where it peaks. Add a second light to see what the pair gives together.
The comparer itself needs JavaScript. Everything it draws is worked from the data described below.
Each light is shown at every channel 100% exactly as its maker's published spectrum graph draws it, read point by point. How that total splits between channels comes from a model of the maker's LED list, fitted to the same graph. A light set with a knob rather than channels is shown at the ends of the knob its maker's graph draws, blended in between, and its page says what was assumed to do that. In the comparer each bar is that band's share of everything the picked lights give, so turning a light down changes its share beside another light but not the shape of a light on its own; the watts, on one scale for every light, are in the table view. Makers' graphs are marketing drawings, so any peak can sit a few nm off.
reeffrags.com is not affiliated with or endorsed by EcoTech Marine, AquaIllumination and Kessil. Each light's page credits the graph its spectrum was read from.
This is an estimate built from a few hobbyists' readings, not a measurement. The range is wide on purpose, because those readings disagree, for some lights by nearly two times, and one owner's corals burned at a step the low end called small. It is for the spot right under the light; anywhere off to the side reads lower. A PAR meter reading beats it every time.