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