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