This is true, and the grayscale images could have a different colored tint when displayed on a Game Boy Color using the palette swapping feature. The white background version found elsewhere in this thread is the closest to what one would expect if we were talking about something printed with the stock Game Boy Printer.
Around 1988 we had this Fisher Price (I think...?) camera that saved to audio cassette. I wish I had any clue where those cassettes are or how to access the images saved on them.
Interesting, from the wiki entry, it appears you would need to playback video from the audio cassettes in the Pixelvision and use a RF Modulator to either view the video on a TV or connect it to a capture device to make a copy.
Is that what it was, Pixelvision? I was pretty young. I assume there would be a way to interpret the data digitally as well without having to use the original device.
Looking at this, it's more interesting than I thought! Wish I had any idea where our original device was, also.