Dark and light blue and orange butterflies again, and x, "the unknown"

This morning, a student was showing me a card game in which each card was divided into two parts like a domino. One of these had a picture, and the other had a number, shape, or color. The card she chose to show me as an example was this:

The butterfly in the center is, you guessed it, a dark blue Morpho menelaus. Right next to it is a light blue butterfly. Above the morpho is a light orange butterfly, and next to that is a dark orange one. These are the four butterfly colors featured in "Another light-and-dark butterfly pair," where they were associated with the word and color amber. Here, the top of the card says yellow, but the color it is written in is pretty clearly amber, not yellow.

It also occurs to me that in the past I've used that same set of four colors to represent the four classical elements: air (light blue), water (dark blue), fire (light orange), and earth (dark orange, which is brown). The idea was that light/dark represented the Aristotelian elemental qualities of hot/cold, while orange/blue stood for dry/moist.

By the way, Debbie has sent me a photo of the orange monarch and blue Morpho menelaus butterflies she mentioned in her comments. Here it is:

During my lunch break today, I was reading Ian Stewart's Why Beauty Is Truth while I waited for my food. When the food arrived, I switched from that physical book to an e-book, The Synchronicity Highway by Trish and Rob MacGregor. (The connection to the present post is that the original Morpho menelaus sync was with Stewart's book and another sync book by the MacGregors.)

On p. 34 of Why Beauty Is Truth, Stewart explains, for the benefit of the genuine layman, some very basic mathematical symbols:

There are three kinds of important symbols for this book, and I'll mention two of them now. One is our old friend x, "the unknown." This symbol stands for a number that we do not yet know, but whose value we are desperately trying to find out.

Minutes later, I was reading in The Synchronicity Highway an interview with the founder of an alien-abductee support group called the Xperiencers. The MacGregors ask about the origin of the name and are told:

Xperiencers is derived from the word experiencers used by Dr. John Mack. I decided to drop the "e" and allow "X" to represent the unknown as is done in solving common equations.