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