![https://www.w3schools.com/colors/colorspicker.asp https://www.w3schools.com/colors/colorspicker.asp](https://innovation.world/wp-content/uploads/2021/06/www.w3schools.comcolorscolors_picker.asp-1000px.jpeg)
Not exactly to chose the best-looking colors schemes, but rather to convert colors codes between the various formats
Hex <-> RGB <-> HSL
(but look at the left menu: you also have colors palettes and other more graphical tools)
Free, No registration, No Download/Install required