Camp Half-Blood Shirt and T-shirts

Camp Half Blood, the fictional sanctuary for demigods in Rick Riordan's Percy Jackson & the Olympians series, is a place where children of Greek gods train and learn to harness their abilities in the face of various mythical dangers. One of the most iconic features of Camp Half Blood is its distinct uniform – an orange t-shirt with a large, bold Camp Half Blood logo on it. But in later books and especially in the fan community, there are mentions of Camp Half Blood shirts being purple. So why are these Camp Half Blood shirts mostly orange and purple, and what do these colors symbolize?