Rainbow spark effect

Rainbow is guaranteed SSR, gold gold sparks are SR. People tend to get them mixed up because they look similar.

Rainbow guaranteed SSR, but gold can be either SR or SSR, depends on your luck...

my recent Musashi and Gramps were both gold Sparks only....but I know its them because there's a "loading" word at the bottom of my screen on the summon page. "Loading" on summon page means u will be getting a servant (or a CE if its a one ring) that you don't currently owned. As I have all the existing SRs and SSRs for saber and assassin classes, I knew the rate up SSR is coming when "loading" appears in both of these instances.

Okay but I've gotten the rainbow spark outside of the GSSR. Last time was on the Gilgamesh banner back in November (when I rolled Gilgamesh ofc)

I'm pretty sure what he meant was that when you get rainbow, it means that card will be a 5 star servant, not that you only get rainbow from the GSSR.