To change the color while still in Apo7x, you can mess with the gradients tab (Two buttons right of the editor button on the top bar, or a tab in the adjustments window) or you can edit the "transform color" value under the colors tab in the editor for an individual transformation.



Post render, I believe you can set the color of an object with the 'Conditional Hue/Saturation' plugin for paint.NET. Instead of shifting the hue, you are also permitted to set it to a color. It also has a fade setting, which might come in handy for any RD wallpapers as it creates a rainbow fill for the selected colors~