Graphic Design or Photoshop help?

I have to create a decorative or thematic cover for my final portfolio in class. I decided to try and design a picture of a bird flying out of a cage and up towards the sun and clouds. I want the bird to be green at first then end up changing from green to maybe yellow, orange, red, and finally ending up with amber. This change of color symbolizes the change I have made over the year and the bird flying out of the cage symbolizes my breaking free (has to do with the assignments in the portfolio) Can anyone help me or give me pointers on how in the world do I design something like this on a computer!!!???