weight painting ruins the form My first time weight painting after rigging.

When I do that, I wanted to color it red, but as I color on the object,

the form changes like sculpting. For example, it suddenly protrudes or deepen.

How can I fix this?
Best way would be to select your mesh then armature using Shift+RightClick then hit Ctrl+P then choose parent with automatic weighting. This will save you time painting everything manually.