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