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