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