I’m aware of this and the post. (Found it, when I started searching for an explanation)
In the (dim) past, there was the “Green Balls” plugin (whatever the precise spelling); we had been using that. I know that it is no longer supported and checked, that we didn’t have it installed before the update of the core. In my understanding, the decision on the color was set by a “colorblind support”-option per user. I can’t no longer see this option; I didn’t check it on the Jenkins 2.277.4.
On 2.277.4 we had been seeing green balls there. (Also the prefered color by our developers)
And as I now realized, while Jenkins core is using the internal icons instead of the ones from “Modern Icon”, the green balls in the build time trend, are still the ones form “Modern Icon”.
Because my interpretation was, that the new icons in the core make “Modern Icon” useless, I wanted to get rid of an unneeded plugin.
For me our current state is ok; I wanted to make others aware, in case they run into the same surprise.