What in the world does that mean?!?!? Yell at a yellow light to stay yellow till you get through it? Yell at the yellow stuff you dripped on your clothes while eating a hot dog? Or the worst—yelling at that yellow stain spreading across your lap after you've laughed too hard at something...
But Yellow is a good thing in this case. It's the final tier and least restrictive of the COVID-19 color tier system. It may be a thing in other states, but it's definitely a thing here in California.
It is estimated that our county (and certainly others) should be moving to the Yellow tier in the next week or two. With the number of COVID-19 cases dropping statewide, Gavinor Newsance claims that the color tier system could be gone, extinct, kaput by June 15. My guess is that once that happens, it means that we'll no longer be under restrictions as to how many people can be in a restaurant, sports facility, theater, theme park, etc. Call it "almost" back to pre-pandemic levels. This doesn't/shouldn't mean that we can let down our guard. Continuing to social distance, wash our hands, and wear face coverings will be a good idea for at least awhile. With more people receiving one of the COVID-19 vaccines now available, we should reach herd immunity, which is a major turning point.
And things should improve significantly from that point on.