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