Names come and go. Look at Mullet and you will see many different paint schemes that companies have used. It gives the buyer something to recognize.
In California we have not Rainbow trout but Planter Rainbow trout.
If the fish are feeding on a certain bait consumers think that they have to have something in that type of baits coloration.
Me? II rarely fish exact looking baits, I want things that stand out. Remember the weak always look different than the healthy.
As for parrot it is a high visibility color. The fish can see it much easier than something that blends in. It also represents a sick or injured bait fish.
Remember your trying to out smart and animal with the brain the size of a pea. Don’t think that hard.