Before
After
- With the rainbow image open, duplicate it.
2. Open Hue/Saturation from Images>Adjustment. Increase Saturation.
3. Use the Rectangular Marquee Tool selecting rainbow area.
4. Open Selective Color from Images>Adjustment. Adjust relative color such as red, yellow and blue.
5. Open a match color image.
6. Open Match color from Images>Adjustment. Adjust Fade.
7. Save the image.
Please view the step by step video: