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