An easy introduction to Blender Compositing, is to make a new node by selecting Use Nodes… and then:
- add a new node from Add > Input > Image and open the texture you want to edit
- add a Color Ramp node from Add > Color > Color Ramp
- add a Viewer node (if not already added) from Add > Output > Viewer
- adjust the properties of Color Ramp to what color you prefer.
- split up the editor window and set the editor type to Image Editor (SHIFT + F10) and select Viewer Node.
- save to a new image/texture from Image > Save As… inside the Image Editor.
New nodes than also be added by pressing SHIFT + A inside the compositor window.