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