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