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