adding breakers to an older panel

The breaker color is irrelevant. It has no effect on the breaker's function.

That said, many FPE Stab-Lok breakers and boxes have been recalled in both the U.S. and Canada and most people familiar with them would recommend you replace the entire panel with something that is less of a fire hazard.

If you do a Google search on your panel you'll very quickly find thousands of warnings about FPE panels & breakers.

I know the color doesn't affect function, was just wondering if the new breakers fit into the old panel.

But, thanks for the tip on FPE Stab-Lok problems. I assume 2014-made Stab-Loks are okay, but existing breakers in my panel might not be. Also I assume its the old breakers, not the panel box or busses, that are the worry - tho I see some websites recomend replacing the entire panel.

Assuming the current breakers are ok may be a mistake. Many of the people looking at them are saying there were no actual changes to the internal workings and the new breakers are just as big of a fire hazard as the older ones were.

Personally, I'd be very leery of leaving the existing box in place but obviously, that's your choice.