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