It's like if someone drew a rainbow with four colors. Or a tree with square leaves. Something is wrong with them.
What really confuses me is the 5-sided snowflakes. I really don't understand where that comes from, and there's pretty much no basis for it in nature other than starfish, which have practically no relation to crystalline structures.
I also get annoyed at restaurants that give children 4 crayons. I understand 3 (primary colors), 6 (primary and secondary colors), and _maybe_ 4 colors if one is black, but I see red, blue, green, and yellow quite often. What happened to orange and purple/violet? Is it really that much more expensive to make two more crayons? It's like they mashed RGB with the primary colors and called it a day. So if you're making a rainbow with 4 colors, I blame restaurants that give out 4 colors of crayons.
Opponent-process theory (https://psyc.ucalgary.ca/PACE/VA-Lab/colourperceptionweb/the...) says that the eye converts the three wavelength inputs into six orthogonal axes (dark-bright, yellow-blue, red-green). From these axes we get the four primary colors: red, yellow, green, blue. Of course things are never so simple. There are various attempts to measure the perception of color (https://www.handprint.com/HP/WCL/vismixmap.html#ncs), and none of them place red-yellow-green-blue exactly along the axes.
Can we agree:
Additive - RGB
Subtractive - RYB / CMY
Thus for trichromats like humans, we use three (or more) primaries for most general purposes. Two primaries would be unable to produce even some of the most common among the named colors. Adding a reasonable choice of the third primary can drastically increase the available gamut, while adding a fourth or fifth may increase the gamut but typically not by as much.
As long as they're different colors, four is all you need.
Baseline, 50% increase in materials costs, unless they make all the crayons correspondingly smaller. New packaging, unless they make the crayons thinner, which solves for the first issue too, I suppose. Modify marketing materials and website. Add a SKU. Make space in the warehouse. Double the cost initially? Then amortize that out as they take a serious bite out of the 4-color crayon pack market... profit! Maybe.