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