What colour is your breast-stroke? Or why synaesthesia is more about ideas than crossed-senses

The interesting thing is how my oldest son has started a "campaign" (among friends and family members) to label "traingles" a color. One of his (less synesthetic) friends tut-tuts the idea saying "traingles are a shape." Since I am always looking for creative versions of things, I wondered out loud if triangle wasn't secretly a scent, which meant it was a taste...something on the more acidic side of things, perhaps lime?