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