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