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