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