Testing color balance and color reproduction with a color checker
Color checkers are boards with colorized tiles, each with a precisely defined color. Having such tiles and the color data we can then use them to set proper color balance for photographs or check how well colors are reproduced by a given camera, or webcam.
For photography you want to take a few additional pictures where the color checker is in focus and next to the photographed target. You can use those shots to create a color balance profile and apply it to actual shots.
When testing cameras, webcams, and other image/video devices you can use such a board to see how well colors are reproduced in given lighting conditions. This is especially handy for devices that do a lot of auto-correction.
Some branded color checkers will have profiles ready to use by popular editing software like Adobe Lightroom. No-name ones will have just raw data, which you will have to use manually.
I got one basic color checker from Aliexpress and it comes in a nice packaging and a color reference table. As you can see there are multiple shapes and sizes available. On top of that, you can notice monochrome test charts with multiple lines and markers - those are used to test focus, image sharpness, imaging circle quality, and achieved resolution.