Guide to transform from color to color in monotonously colored images, in this example make a wood texture the same color as another one in GIMP: 
- First open both of your images as files
- Use the color picker tool (O) with "Sample average" enabled and set to something reasonably high to get the average color of your image
- Open your image you want to transform
- Add a layer with the average source color first
- Then add another layer with the replacement color next
- Set the replacement color layer blend mode to "Divide" 
- Click on your replacement layer and "Merge Down"
- Set the blend mode of the new merged layer to "Divide"
- done, you have now transformed your image from one color to another 
TIP: you can make your source image grayscale first to avoid hue issues and have a more uniform result if desired 
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