In our area, we use what is called blues for walleyes. The bait shops all have the minnows in blue water. This helps keep the bluish tint to the minnows. I use a blue bucket for the minnows on the lake. If I use a white bucket, with in a day the minnows are a dull white color. I guess the blue keeps the blue pigment in the skin of the minnow.
Harry