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