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)(13,14,17,20)(15,19,16,18)(23,27)(26,28)(6,10)(7,12)(15,16)(18,19)(22,25)(26,28) involution — undirected(6,10)(8,11)(13,15,17,16)(14,18,20,19)(21,22)(23,26)(24,25)(27,28)(1,2)(3,4)(5,7)(6,11)(8,10)(9,12)(13,16,17,15)(14,19,20,18)(5,8,9,11)(6,7,10,12)(13,14)(15,18)(16,19)(17,20)(21,23)(22,26)(24,27)(25,28)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.