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