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