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