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