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