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