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