If you go to this link you should be able to find what you need.
GoRotax
Yeah, been there, they don’t make it easy either. Did find a tech update from last year “recommending” yellow backgrounds but nothing definite.
This is for PanAm. Thanks for the link, this is pretty clear.
You didn’t say which event you are racing at, but if it is an international level Rotax event, you need yellow background with black numbers. Go to CIK-FIA and check out the tech regs 2.24. http://www.cikfia.com/fileadmin/content/REGULATIONS/Technical/Technical%20Regulations/Web_RT_FULL.pdf
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