Tool itself can have insufficient contrast

[missmatsuko]

Since the background color changes based on the colors being compared, the tool itself can fail WCAG contrast requirements.

When I compared #C4C4C4 and #FFFFFF, the page heading ("colour contrast checker) and HSL sliders fail contrast requirements:

In this example, the background colour is #C4C4C4 (contrast of 1.74 to background), the heading color is #FFFFFF, and the slider bars are #939393 (contrast of 1.76 to background).

I would recommend not changing the whole tool's background colour, and having a preview swatch instead.

[bryanjonker-illinois]

Second this. This is a great tool but I can't read the copy when the accessibility is poor.