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