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