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