Producing Chlorophyll is a nitrogen intensive process, so it is important for healthy green plants. It is possible to limit nitrogen in the planted tanks to produce red plants due to the red pigments coming in to play more. I did this with Rotala rotundifolia:
However, N is a very important nutrient nestling in behind light and carbon in terms of importance of healthy plant growth. If in insufficient amounts, that plant health will suffer and kick off an algae outbreak.
In low light tanks, sufficient low and stable levels of N can be available from fish waste (NH4) or as NO3 at the end product of the nitrogen cycle. In tanks of increasing light, N will need to be added via KNO3 to prevent stunting of plant growth, poor health and, ultimately, algae. To promote zero nitrates in a planted aquarium is a risky business, and not one I would necessarily advocate.
NOTE: It is not the intensive light that turns plants red. When my Rotala rotundifolia grows above the water´s surface it turns back to green, yet it is in even more intense light.
Dave.
........ practically perfect 
