Usually you’d just paint them all at once. It’s not a huge ordeal for most bikes, the gas tank is typically removable.

I would imagine a body shop will be able to match any color you want but the price is probably going to be a put off, just to prep and shoot paint on a motorcycle gas tank. I would look into doing it yourself first using the body color paints designed for auto touch up work.
What about the frame? that will look odd if it is different from the rest wouldn’t it?

You can remove the gas tank on a bike almost as easily as you can remove the fairings… But I would not say your strategy is very cost effective… another thing to consider would be just putting vinyl over the original parts, that way you can change the color to whatever you want, and if it scratches or chips, you just peel the vinyl off and put another layer on.

It’s also cheaper than buying addt’l fairings and paint… and you don’t have to worry about being able to find the parts.

Do the people who tell you to “just buy new fairings’’ do they realize that:

1) Fairings for most sport bikes are pretty expensive? (Roughly $800 to $1K for all new fairings your basic everyday sport bike: Suzuki, Kawasaki, Yamaha)

2) When you buy new fairings, they come like this and need to be painted anyway?

You’d spend a lot less money ordering a bike with a color you already enjoy. If you want to paint it something crazy and not factory, you’d save a ton by just painting the parts you already have and not wasting money on a second set of fairings.