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)(13,14,17,18)(15,21,23,19)(16,20,25,26)(22,24,28,27)(5,7,9,8)(6,10,11,12)(13,15,17,23)(14,19,18,21)(16,24,25,27)(20,22,26,28)(2,4)(5,8,9,7)(6,10,11,12)(14,18)(15,21)(19,23)(20,26)(22,24)(27,28)(13,16)(14,20)(15,22)(17,25)(18,26)(19,27)(21,24)(23,28) involution — undirected(13,14,17,18)(15,19,23,21)(16,20,25,26)(22,27,28,24)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.