Fade
Line colours, fill colours and text colours can be faded (transparency increased) using Edit->Adjust Colour->Fade Alpha. Only selected paths and text areas will be affected. If you want to fade a bitmap you will need to use a bitmap editor that provides that function.
See also:
- Reducing to Grey Scale
- Colour Space Conversions
- Removing Translucency
- Line Colour
- Fill Colour
- Text Colour