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