Are the lighter Baltic amber colors more powerful than the darker colors?

​Yes, and additionally the raw colors are stronger than polished.  The following scale will give you an arbitrary idea of the range of effectiveness, using a scale from 1-10. All Baltic amber colors work well for teething pain, but some colors may be better if dealing with chronic pain levels. 

11 White <- Goes up to 11!
10 Milk 
10 Butter
9 Lemon
9 Butterscotch
9 Nutmeg & Lemon
9 Milk & Honey
8 Honey
8 Nutmeg
8 Multicolored 
8 Lemon & Cognac
7 Mixed Honey
7 Lemon & Cherry
7 Rainbow
7 Cognac
6 Dark Cherry
6 Dark Green