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