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