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