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