The Colorize tool renders the active layer or selection into a greyscale image seen through a colored glass. You can use it to give a “Sepia” effect to your image. See 色彩模型 for Hue, Saturation, Luminosity.
You can get to the Colorize tool in two ways:
In the the image-menu through: → → or → ,
          or by clicking the tool icon:
          
             in Toolbox, provided that you have installed color tools in Toolbox.
          For this, go to
          Tools Dialog.
          
          in Toolbox, provided that you have installed color tools in Toolbox.
          For this, go to
          Tools Dialog.
        
            You can save the color settings of your image by clicking the
             button
            
               
            
          
            The
            
               button opens a menu:
            
            button opens a menu:
          
which lets you Import Settings from File or Export Settings to File, and gives you access to the Manage Save Settings dialog:
Hue: The slider and the numeric text box allow you to select a hue in the HSV color circle (0 - 360).
Saturation: The slider and the input box allows you to select a saturation: 0 through 100.
Lightness : The slider and the text box allow you to select a value: -100 (dark) through 100 (light).
The Preview button makes all changes dynamically so that they can be viewed immediately.