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