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