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