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