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