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