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