I recently encountered a few recipes where food is not allowed to 'get colour', or become brownish while baking. A few examples of what I mean:

• Chicken turns a golden-brown colour.
• Burgers get a very dark crust.
• Unions turn brown.

How do I avoid my food becoming this colour when cooking? Is there a way that works in general or if not, a way to find out how to do this for the food I am cooking today?

Specifically, in this recipe for white asparagus panna cotta, a brown colour is undesired.

Bak de asperges een minuutje of 5; ze mogen niet kleuren!
Cook the asparagus for less than 5 minutes; ensure they don't change colour!