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