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