Yellow for a few minutes or a few seconds upon awakening? Perhaps the visual areas of your brain were still busy working on the hallucinatory world of lucid dreams whilst partially dealing with sensory input from the real world. I wouldn't worry about it. Feel free to control your dreams as I do not think such practice has anything to do with the peculiarity you experienced.
Just curious: Are you on any medication, drugs, or suffer from any type of mental afflication?[ Post made via Android ]
"Empty cognizance of one taste, suffused with knowing, is your unmistaken nature, the uncontrived original state. when not altering what is, allow it to be as it is, and the awakened state is right now spontaneously present."