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