Safety relay color

Hi Colleagues
There are a norm about color for safety relays?
Some are red (AB) others are yellow (pilz) and others are brown or dark (ABB with a red band). Does color have a meanning?

I don't believe so.

I've seen Red (AB, Banner)
Yellow (PILZ)
Green (PILZ)
Yellow/Green (Leuze)
Black (Schmersal)
Brown/Yellow/Red (ABB/Jokab)

I don't think the color carries any significance beyond the brand's design.

Thanks Tharon for your answer. I think so but it is good to know that others see the same way.