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