Exodus 28:31
"And you will make the robe of the ephod totally of blue [yarn].
Exodus 28:4
And these are the garments that they will make: A breast piece and an ephod and a robe and a tunic of specially woven fabric, a turban and a sash. And they will make holy garments for Aaron your brother, and for his sons to serve as priests for me.
Exodus 28:28
And they will tie the breast piece by its rings to the rings of the ephod with a blue cord to be on the waistband of the ephod, and the breast piece will not come loose from the ephod.
Exodus 39:22-26
And he made the robe of the ephod, weaver's work, totally of blue [yarn].
Leviticus 8:7
Then he put the tunic on him and tied the sash [around] him; then he clothed him with the robe and put the ephod on him; then he tied the ephod's waistband [around] him and fastened [the ephod] to him with it.