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