Selectedtovertexcolor is a Blender add-on for setting the vertex color of objects in your scene. It's built to help create an ID-map or to visually colorize objects and vertices quickly in different colors, without switching back and forth to vertex color mode.
In Object Mode, all selected objects can take the same color of your choice, whether you're working with one object or several at a time, and you can also give each selected object a different random color. In Edit Mode, selected vertices receive a chosen color, with an option to colorize sharp regions or apply smooth color transitions. You can repeat the process to use different colors on other objects or vertices.
Everything runs from a single click or a customizable keyboard shortcut. The add-on includes documentation, works across Blender 2.8 through 3.2, and is distributed under the GPL license. A demo video is also available.