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