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