One vertex per element, one color per generator, with an edge from x to x·s.
(2,3)(6,9)(7,11)(13,14,16,18)(15,17,20,19)(21,22,26,25)(23,27,28,24)(13,14)(15,17)(16,18)(19,20)(21,23)(22,24)(25,27)(26,28) involution — undirected(1,2,4,3)(5,6)(7,10)(8,9)(11,12)(13,14)(15,19)(16,18)(17,20)(21,24,26,27)(22,23,25,28)(5,6)(7,10)(8,9)(11,12)(13,15,16,20)(14,17,18,19)(21,25,26,22)(23,27,28,24)(1,3,4,2)(5,7,8,11)(6,10,9,12)(13,14)(15,19)(16,18)(17,20)(21,23)(22,27)(24,25)(26,28)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.