Black.
Seriously, though, I own four ukulele bags with this or very similar patterns that I
really like. How the exterior material would fare on a tuba bag is anyone's guess, but if it was only on the main, outer panel I think a responsible person would see it last for many years. If I could get a full-Cordura bag body with reinforcing leather contact patches AND with this banket material installed
on top of the Cordura on the main face of the bag I would get one as soon as I could afford it. I might get as many as four of them, depending on the price.
I am not "in" to bright colors at all, but am into dense patterns with dark or muted colors.
Teal? Puce? Chartreuse? No thank you.
This blanket-looking stuff? Heck yeah. Take my money.
This is just a random image from a quick Google image search. It is similar to what I like. The material looks like it might be fuzzy, and therefore, easy to mess up if you use it a lot or if it gets wet. But that sort of pattern is still very cool and I would likely purchase something like this, skinned over a Cordura shell.
This is an actual bag I own. It is a sales image from Amazon, but my bag is itendtical in the material, which is some tightly woven industrial grade fiber that is not all warm and soft like a blanket, but it looks great (well, to ME, that is) and has survived a number of rainy days and lots of direct sunlight over the years I have owned it. A tough, long-lived Cordura bag with the outer panel skinned with this material in this pattern would cause me to empty my pockets in a huge vomit of filthy lucre. No joke. I have been waiting for such a bag for years.
Pretty weird, I know. But you asked, and are a good enough businessman to at least listen to the more… let's say "esoteric"… customer feedback.
Thanks for listening, and not laughing directly in my face.
PS - Yes, I know this sort of woven stuff would tend to snag, if the owner is careless. I am not careless with my gear, and know that many here are also not careless. Having the sides and the strap-bearing face made from genuine Cordura would cover just about all "wounds" as the outer panel does not come into contact with all that much - again - if the owner is careful.