Exodus 28:28

28:28 They are to tie the breastpiece by its rings to the rings of the ephod by blue cord, so that it may be above the waistband of the ephod, and so that the breastpiece will not be loose from the ephod.

Exodus 28:31

28:31 “You are to make the robe of the ephod completely blue.

Exodus 28:37

28:37 You are to attach to it a blue cord so that it will be on the turban; it is to be on the front of the turban,