The colour of the mug itself can make the coffee taste different, and each colour has its own taste attributes. You can even alter the way your coffee tastes during the day, just by changing your cup!
White mugs have been associated with bitterness in coffee. Many people object to coffee because it is bitter, but many other people would prefer to drink a more bitter coffee in the morning. The coffee mug that you are using in the morning should be white so that you will have a pick-me-up in the morning.
Red and Blue
You can get more sweetness out of your coffee when you are drinking from a blue or red mug. These colours are often associated with sweet fruits, and it is possible that the brain translates that association into sweetness when you are drinking the coffee. This is the best way to enjoy coffee as you are drinking it though the day.
Many people perceive the strength of the coffee base on the colour of the coffee. This judgement is not always correct, but it is something that people taste when they drink the coffee. When you are drinking from a mug that makes the colour more powerful, you tend to think the coffee is much stronger. This is why a white mug creates a bitter taste in the coffee while glass mugs make the colour seem more muddy.