If you care about accurate color, you do use a card with "whole bunch of patches" of different colors. For example, these British Library guidelines on photographing and scanning archival material say:
"An industry-approved colour chart or greyscale reference card is essential in order to check the accuracy of the colour captured in the photographs. This is a physical card that is available to purchase on the internet. It cannot be downloaded from the internet and printed, or inserted into your image using software. Approved colour checkers that have been used in EAP projects include: Gretag Macbeth ColorChecker, QP cards, Kodak Color Control Q13 card, Past Horizons Bookmark Photo Scale."
(https://eap.bl.uk/sites/default/files/Guidelines%20for%20pho...)
ColorChecker (“Macbeth”) Chart: https://poynton.ca/notes/color/GretagMacbeth-ColorChecker.ht...
QP cards: https://www.argraph.com/QP202.html
Kodak Q13: https://www.kodak.com/en/motion/page/color-separation-guides...
Bookmark photo scale: https://www.pasthorizonstools.com/Photo_scale_bookmark_p/boo...