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