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