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