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