I cannot believe, seriously, that anyone who deals with Excel spreadsheets on a regular basis that have as their primary purpose doing numeric calculations could ever propose that having a screen reader read just what's on view for a numeric cell, when what's on view would be interpreted by a sighted user in one and only one way, and a way that is completely the opposite of what's on display if the conventional use of "red" for negative is intentionally ignored.
The numeric value of a numeric cell is essential if the data is to have any meaning that everyone, blind or sighted, will interpret correctly. Since the blind cannot possibly interpret color in the same way as a sighted person would for red values in a spreadsheet, what's essential is that they are clearly given the actual information that the color represents to a sighted user. It's just that simple.
Brian - Windows 10 Home, 64-Bit, Version 1809, Build 17763
The terrible state of public education has paid huge dividends in ignorance. Huge. We now have a country that can be told blatant lies — easily checkable, blatant lies — and I’m not talking about the covert workings of the CIA. When we have a terrorist attack, on September 11, 2001 with 19 men — 15 of them are Saudis — and five minutes later the whole country thinks they’re from Iraq — how can you have faith in the public? This is an easily checkable fact. The whole country is like the O.J. Simpson jurors.
~ Fran Lebowitz in Ruminator Magazine interview with Susannah McNeely (Aug/Sept 2005)