Here's a fun exercise: take a look at the labels for mass market consumer products you have around (especially ones printed on cardboard or paper), and try to figure out how many colors of ink were used to print them and what the colors were. Spoiler: almost none of them will have been printed with (just) the standard CMYK colors.

For bonus points, see if you can spot (color) registration marks on the labels. Generally these are little circles of color and sometimes + marks as well.