ℹ️ There is a new version featuring the current color scheme: https://scratch.mit.edu/projects/870579908/ I often find myself wanting to use colors from the Scratch color scheme - especially when I make projects related to Scratch itself. This project contains a sprite with a costume displaying those colors. If you put it in your backpack you'll have access to the colors whenever you need it.
By "dropdown-input" I mean the round-ended dropdown which you can put reporter blocks in. Thanks to @gregatku for spotting the missing "My Blocks" colors. Thanks to @Cra_Z-Animates and @JYHK426 for helping me realize that the outline colors are the same as the slot colors, and that there is a third color: the dropdown-inputs.