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