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