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