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