A tool for creating CSS color palettes for web UIs that pass WCAG accessibility standards for color contrast, where you can fine tweak all the tints/shades quickly using a hue/saturation/lightness curve editing interface:

https://www.inclusivecolors.com/

Unlike most tools based around autogenerating colors, this is more of an editor that lets you fully customise all the tint/shades to your liking with a focus on accessibility. This is important when you've got existing brand colors to include and want to find accessible color combinations that work together.

Would love feedback in general and especially from designers/devs who have different needs in how they go about creating branded palettes!