QUICK ANSWERStart with the tool that matches your immediate input.
Open Posterize Image first when its stated purpose matches the result you need now. Use Remove a Color from Image only when it solves a separate next task.
This guide is for creators, marketers, designers, and website owners. Start with Posterize Image when your immediate task is to use the Posterize Image to complete this file task privately in your browser. Move to Remove a Color from Image only when you also need to use the Remove a Color from Image to complete this file task privately in your browser.
The goal is not to run two tools automatically. It is to finish the first narrow task, inspect its result, and then decide whether Remove a Color from Image solves a genuinely different next step.
Both tools sit in Image & Design, but they handle different inputs or outcomes. Keeping those roles separate reduces repeated work and makes verification easier.