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