One vertex per element, one color per generator, with an edge from x to x·s.
(2,4)(5,6)(7,9)(8,10)(11,12)(13,14)(15,19)(16,21)(17,20)(18,22)(23,26)(24,28)(25,27) involution — undirected(1,2)(3,4)(5,6)(7,11)(8,10)(9,12)(13,15,18,17)(14,19,22,20)(16,23,24,25)(21,26,28,27)(5,7,8,12)(6,9,10,11)(14,20)(15,17)(16,24)(19,22)(21,26)(27,28)(2,4)(7,12)(9,11)(13,16)(14,21)(15,23)(17,25)(18,24)(19,26)(20,27)(22,28) involution — undirected(6,10)(9,11)(13,15,18,17)(14,20,22,19)(16,25,24,23)(21,26,28,27)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.