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