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