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