Reddish rusty orange would be MMT octane booster, but that's not legal for the street. Racing only. And this isn't that color.
Not sure about the yellow. Could be sulfur, but the US has had lower sulfur regulations for years. Unless there has been an extreme weather event like a hurricane and a refinery had a burp and the regulators said sell it anyway because it's an emergency and we don't want people running out. But that would be rare.
I had oil issues on an an old Honda a few years back that would make the engine misfire, but that gave white fluffy deposits. But that engine was fuel injected and the air-fuel ratio would not have been rich.
It might just be an early look at a carbon deposit that is about to turn black.
EDIT: Bosch says yellow comes from lead. Did anyone slip you some avgas? :-)
A little light yellow is normal, they say.
https://www.boschautoparts.com/docum...2-1dadd0d5def6