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