Right Chris and, if I remember well, importing an old UVN / UVD voice format from Tyros4, also in this case the icon becomes yellow, but you can play it / edit it on all YEM compatible instruments like a "normal background" voice. I'm ready to edit this post if I'm wrong!
Francesco
Yes, you are right, Francesco! Imported UVN/UVD voices are also "yellow/orange" in the YEM. This can be avoided by importing the UVN/UVD files in question into "Awave Studio" and then saving in SF2 format (with "Save selected instrument as ..."). This SF2 file can then be imported into the YEM (e.g. as "content" into an existing Pack) without the icon being "yellow/orange".

I was only referring to the post from "tolica78" (where he wrote "
I created the voice in Yem and with new waves and also turning yellow!? Dont know.")
So I assumed that his question mainly relates to newly created Custom Voices (by him), not to imported Tyros3/4 UVN/UVD Voices or already "yellow/orange" Voices from existing .ppf Packs.

Best regards,
Chris