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