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