Open your image in Paintshop Pro. I’m using the image below:

Make a New Raster by going to Layers > New Raster Layer. A box will pop up. just click OK.

Now go to your Material Pallete, set the colors and click the Gradient Icon.

A box will pop up. Play with the gradient style then click OK.

Click the Flood Fill icon and fill your image.
After filling the image with your gradient, go to Layers > Properties. A box will pop up. Set the Blend Mode to Hue then click ok.

You’re done!

Save your work.