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