is it appropriate to wear a Wallace Red Modern to a funeral

[Tobus]

By your username and the mention of tights, I'm assuming you are female. I agree that the colour of the tartan has no bearing on appropriateness when it comes to traditional Scottish stuff, but in this case any perceived inappropriateness would likely come from the fact that it is a skirt being worn with a hemline above the knee. Depending on where you live, and the social mores of the attendees at the funeral, wearing an above-the-knee skirt might seem inappropriate for a funeral. It's really hard to say without knowing how these things are perceived in your area, and by the age group and social proclivities of this particular crowd.

Even down here in Texas, I've been to funerals where folks dressed casually or even wearing tie-dye outfits (to honor the death of a somewhat eccentric fellow), where a short tartan skirt would be perfectly appropriate. But more often than not, the funerals I have attended were for well-established older religious folks, and the attendees were dressed very conservatively. A female in a short skirt would have drawn raised eyebrows, tartan or not.

No one here can really give you an accurate answer without knowing the people or culture who will be at the funeral. There is no universal rule on this.