Purely Instrumental Music at Mass of Christian Burial?

Certainly not the liturgical hill on which I'd care to die.

And even less so, say, flowers, since there are, [or so ISTM, I've never looked them up since they have never been my purview in any situation,] contradictory instructions, or rather, contradictory traditions, since the OCF currently in force allows for them.

I would not be hard-nosed about anyone of this, were I advising or helping mourners.

Where I AM inclined to hard-nosedness is with "authorities" misstating liturgical law to reflect their inclinations, and passing off their preferences or opinions as rubrics.

What are the liturgical colors for a funeral Mass?

White. The liturgical color chosen for funerals should express Christian hope but should not be offensive to human grief or sorrow. In the United States, normally a white vestment is worn at the funeral rites and at other offices and Masses for the dead.

Um, no, liturgists of St John's Chelmsford.

GIRM, Chapter VI

346 As regards the color of sacred vestments, traditional usage should be observed, namely:  .......

d) The color violet or purple is used in Advent and Lent. It may also be worn in Offices and Masses for the Dead.

e) Besides the color violet, the colors white or black may be used at funeral services and at other Offices and Masses for the Dead in the Dioceses of the United States of America.

Please, please, please, black at my funeral, and violet if inky vestments aren't to be found.