You would be surprised how many times you might want to change the color of something in post-production. This video shows you how to do it quickly and easily in Adobe Lightroom.
Before I started, I couldn't have imagined how many times I would need to change the color of things in my commercial photography. I thought that I would just get the right model, props, clothes, and so on, and that would be that. This was naive. In actuality, I have often had to shoot without every color in the frame perfect, and then change it in post.
If you'd asked me ten years ago, I would have doubled down my position on not needing to change colors when it comes to hair. Then, I had a brief land in my inbox which wanted a specific type of portrait and I had an image already shot that would be a great fit. There were two issues, however: firstly, they wanted it in the snow and I shot it in high summer. This was easily fixed as the image had a shallow depth of field, so I just made some color tweaks and then added some blurry snowflakes. Secondly, they wanted a redhead and my model was blonde. Again, I fixed it with some color editing and the image was suddenly exactly what they were after.
You don't often need to edit hair colors, at least in my experience, but the tools to do it are worth having!