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