I'm not sure if there is really a difference designated by the color other than to indicate it is a chaser strike. Blue seemed to be the most popular chaser color until last year. Since then, it seems like casinos are using red. Perhaps that's because the new machines have the capability to dispense both $10 and $40 strikes. At the El Cortez, when they installed the first ever new style machine, they used red for the $10 chaser and blue for the $40 chaser. So maybe there is now a system. Someone else might know. In another post, someone talked about orange being a new one in the future with a specific meaning.

You don't see many yellow caps for sale because only two casinos issued them, and in very small mintages: O'Shea's Elephant/Donkey combo and Plaza Your Place in Town. They sell for $400-600 since they were limited to 125 and 100 mintages respectively.

The only pink caps I know of were from Slots-A-Fun. They did two issues in pink before switching to reds.

Most casinos display the strikes currently in the machine at the top and sides of the dispensing cylinders. So you know what is generally being offered in the red caps. But given that you only see the edge of the strike in the tube, you don't know till you get it which red cap you won, if there's more than one in the machine. I think the immediate gratification of seeing what you get via a translucent red cap is better than having to open an opaque gold or silver cap. Also, I don't think strikers will want to display it at home in a cap you can't see through. Why not change it to clear at home you might ask? Many collectors like to keep the colored cap on to differentiate it in their collection. If they are insistent on keeping their chasers in airtights, they might dye a clear airtight to the same color as the original cap that came out of the machine.

--Norm