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