Hello Wings:
It is great that you were able to see your deceased loved ones as you did.
I'm not certain how to define each color, but certainly white light is a really good thing.
How big was your father's light? Was it a point of light? If so, you might've been seeing it through your crown chakra (at the top of your head).
Since your brother's light was bigger, it is possible that you saw it through your third eye, which might explain why you saw a mixture of colors. What colors did you see?
Many other people have seen the spirits of loved ones shortly after they passed away. The fact of how they are able to be around so soon, possibly shows how the realm of no time (the spirit World) interacts the realm of time (the physical World). I say this, because so soon after passing away, your father was able to reflect white light. I have read of other cases where spirits appear in such a pure form shortly after their death.