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