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