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