Can't paint or select bones in weight paint mode

Question

I just started using Blender and started a little project. I made a model and the bones myself. I used the automatic weight when parenting the armature and the model.

When I moved the legs in pose mode, the middle body bent so I thought I will just go weight painting and make some adjustments. But the model is mostly grey in weight paint mode. The bones are grey also when selected. Just a tiny bit of color is visible near the selected bone.

I tested with a cube and it worked well. I have been trying to find a similar case from the internet but have not seen one. Thank you for the help.

Answer 1

You have the Face Mask activated. It's a mode that allows you to only paint on whatever faces have already been selected when you were last in Edit Mode. It's activated by the button near the red arrow shown here. Click it again to return to the more deeply colored standard weight paint mode.

Answer 2

Weight painting is entirely for meshes as far as I know, and is a way of defining which vertices connect to what bones. Do not try to select bones and then go into weight paint on the mesh. That’s not how it works. Look at the properties editor, on the mesh tab. Somewhere, there will be a panel about vertex groups. Look at that panel, and you will see a list of vertex groups on your mash, one for each bone. When you click a vertex group in this list in weight paint, the 3-D view port will show you what vertices are strongly weighted in this group, not very much weighted in this group, and either have a membership weight of 0 or are not in this group at all (virtually the same effect), with color gradient. As a warning, even if vertices have only a little bit of weight in one group, but they are not in any other groups, they will totally move with that one group’s bone rather than mostly standing still.

On a sidenote, the color scheme for your weight painting seems a little bit dulled. Have you changed user preferences at all?