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