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