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