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