Blender weight painting I'm new to blender so this might be a noob question!
I've been trying to weight paint as the automatic weighting was affecting the wrong parts of my mesh, however, nothing I'm doing seems to be changing anything! I've darkened all the areas I don't want my bone to affect and brightened the areas I do but when I go back into pose mode it's as if I've done nothing. 

For example, here I painted the foot and darkened the other.



And here is the result - as if the painting hasn't been applied, am I missing something?
When you get that kind of trouble it is usually a second bone causing another extra influence on the area you´re presenting. Scroll-select each vertex group on your bone´s vertex groups. Surely you will find a second other bone causing an additional influence.
Also, make sure the paw bone is set it´s influence to 100% (completely red).