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