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