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