It’s so weird to me to think that Photoshop started life on the decidedly black-and-white Macintosh.
Just to be clear, Photoshop 1.0 definitely required (or at least supported) Color QuickDraw. I vaguely remember the unreleased product was grayscale, but I don’t think that ever shipped. You just mean how the Mac itself started as a monochrome device?
I could’ve sworn that Photoshop 1.0 would run on a monochrome Mac (though it recommended a color one), and would support color printing regardless.
However it looks as though 1.0 required at a minimum a Macintosh II, which supported color.
I think I’m misremembering because I read a history of Photoshop article and they talked about earlier products from Adobe doing clever things with 1-but dithering.
I used Photoshop on a black & white classic Macintosh in 1992, after first using it on a Mac II in 1990. It wasn’t fast but it did work. Images on screen were dithered for display.
Photoshop dithered for display until 24bit colour displays became standard.
I remember using it on an LC475 in 1995 and my memory is of the about screen being B&W too. I guess memory is unreliable though, that’s probably nonsense ‘cos it was on System 7.1 which was definitely color. In summary, dunno.