it really is spring

Seems my backyard is one of the last places that shows signs of spring. my tulips are finally starting to open up. yeah. funny thing on the tulips. the back yard retaining wall is split by a staircase. I planted a mix bag of tulips several years ago and when they came up one side of the wall has a variety of color the other side is ALL this purple color. how does that happen? I wonder if the soil is different on one side or could I have had some really strange luck and pick all the purple bulbs and put them on one side. no telling I guess.