Fill Color is a simple tool for filling color on the texture by selected faces.
It use the selected faces geometry to determine the area to fill color.

Using this tool, you don't need to create new material for each color and do baking for the final texture map !

The tool do the following :

1. If there is an existing Material and Image node connected, the tool will take the first material of the object, and use the connected image texture for painting. (If there is no material, the tool will create a new material and new image)
2. It fill the color to the UV coodinates of the target faces.
3. You can set the "margin" of the filling, so the color show up smoothly on the mesh borders. When you do UV unwrap, make sure that you have set the margin between UV islands.

You just need to switch to "Edit Mode" , select the face, then run the tool.
Select color and margin.

Usage

Switch to Blender "Texture Paint" mode , or any Modeling / Layout mode with "Material preview" using Z key.

Then, when you want to use the tool, press Tab key to swicth to Edit mode,

Switch the Face select mode,

Select the faces, then right click inside the viewport,

Select "Fill Color" from the bottom of the pop up Context Menu. (I suggest adding it to the Quick Favourites menu of blender)

Then you can open the setting from the Bottom Left of the viewport screen.

( Note : On the first use, the tool will install python image library from PIP, so it will wait for about 10 seconds. After that it doesn't need. )

There are few settings :

Margin : The very small margin for over-filling. That means the tool can fill the color more than the face area. The reason is that, when you UV unwrap the mesh with margin space, then you can paint over it to ensure smooth transition of color for sharp mesh borders.

Color : Click the the color to open the color picker.

Clear Selection : For easier to view the color, it is better to remove the selection for the faces.

Use Brush Color : This is a very useful option for painting the model by Color Palette of blender. When you use blender's Paint Texture mode, you can build your brush's color pallete on right hand-side sidebar. Then you can use this addon with "Use Brush Color" on. You can easily switch between your colors.

Updates

Version 1.1.0

• Clear selection after filling color (for better visibility)
• Option to use blender's Brush Color from color palette. Just open the Right-side panel of Texture-Paint view, select color, then run Fill Color.

This addon is free !

Enjoy ! : )

https://x.com/kushirosea