To invert the colors of a photo on your Windows or Mac device, download PhotoDirector and follow along with the steps below:
Click on Adjustment from the top menu.
Underneath Adjustment will be two options: Manual and Preset. Click on Manual.
Scroll down until you see Curve.
Choose RGB to invert all the colors in the photo, R to only invert red, G for green, or B for blue.
Click on the bottom left of the line running through the curve and drag it to the top. Then click on the top right of the line and drag it to the bottom.