Firstly the life span - Minnows can live upto 8 years in optimum conditions although they are usually eaten by this time, however in a garden pond there are less predators so around 2-5 years a more likely estimate in a pond.
Breeding time - Breeding occurs between april to june in the wild, depending on your pond size and depth will alter this slightly.
Colour - Yes it is obviouse, in the breeding season the males develop darker features such as their back, their sides become a deep gold, and their belly becomes dark red, Males also develop tubercles on their heads when in breeding season, minnows are sexually mature at 1 year of age.
Eggs are scattered on the bottom as far as im aware breeding can take several days
hope this helps
