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)(15,20)(16,18)(17,19) involution — undirected(1,2,4,3)(13,15,17,16)(14,18,19,20)(22,26)(27,28)(2,3)(15,16)(18,20)(21,22,25,26)(23,27,24,28)(5,6,8,9)(7,10,11,12)(13,14)(15,20)(16,18)(17,19)(21,23,25,24)(22,27,26,28)(1,3,4,2)(5,7,8,11)(6,10,9,12)(13,16,17,15)(14,18,19,20)(21,24,25,23)(22,28,26,27)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.