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