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