I received money to replace my gutter but not my downspouts, I received money for painting so my downspouts and gutters match. Can I use that money to put towards downspouts instead and just pay the difference?
You can generally use the money any way you wish. However, if you do not replace your gutter and paint it to match, you will not subsequently be able to make an additional insurance claim in this regard.
As far as the insurance company is concerned, you have been made whole once they paid you. If you used the money for a vacation, the insurance company probably wouldn't care. But, if you did that, you couldn't subsequently claim roof damage caused by your damaged gutter, because that's your fault for not fixing it.
When making a claim and getting money from that claim you can run into paperwork issues.
I have seen it when you have a mortgage. The insurance company will send a check to the mortgage company or to you with the requirement that the mortgage company also has to sign the check. The mortgage company will only release the funds when you send them a bill for the repair. The mortgage company will do this to protect the collateral.
Sometimes the insurance company will ask for a proof of the repair. They will do this if in a later year you make a claim for damage in the same area.
It is unlikely that the mortgage company or the insurance company care about matching paint colors. But if you did the opposite: you didn't replace the downspouts and instead spent money on matching paint colors, then they could deny a later claim if the damaged downspouts led to other damage.
Yes, that is absolutely fine.
In general you don't have to use insurance money to replace whatever was lost. You can use the money to go on a nice holiday instead.
With roofing, gutters, and similar things there is an issue that if you don't replace them, then this can lead to further damage to the property which may upset your mortgage company and the insurance company won't pay for that subsequent damage (because you didn't keep the property maintained. None of this applies in this case, because you are going to keep the property maintained.