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