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