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