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