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