This image was created by Stable Diffusion with the following prompt:
Prompt – side view of a parked super car from far away, zoomed out
Negative prompts – (worst quality, low quality, normal quality:1.8)
Select the red region with Quick Selection Tool, and go to [Image -> Adjustments -> Hue/Saturation].
Click ‘Colorize’, and try adjusting Hue, Saturation, and Lightness.
Here is another result. There are other methods to change only a certain part of the colors in Photoshop, and this is so far the easiest method available. 🙂
The trickiest part of this method is selecting the region of the image in the beginning, and there is an easier method for that as well. Go to [Select -> Color Range] to select red, and use the Add to Sample brush (the brush with a plus icon) to expand the selection.
This is the end of the tutorial. 🙂