It's a good question. I remember tau can see uv spectrum. And that they are alien. It stands to reason they would put differing values on color then humans.
Humans caution tape is akin to a wasp. Yellow often in nature is a warming.
I painted a colony security force in my project log. Instead of red white and blue I use purple white in blue.viewtopic.php?f=46&t=26263
Perhaps green? A bright yellow green could be caution?