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