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