Hi Andy,
We might need more info about your exact situation.
But all red means that it is already at 100% weight (and you can’t add any more)
In the video when you see the colour change from bright pink (or magenta) to Blueish – that’s because I had a bone selected that didn’t have an existing weight group at first, but then when I ‘added’ weight to it, Blender created the group and coloured the weights according to my painting.
Magenta (or pink) = the group doesn’t exist.
Blue = group does exist but that part is not being influenced
Red = 100% influence in the active group
If the subtract brush isn’t working it might be the settings. Turn the weight up to 1.0 and the strength up to 1.0 and then paint on the red portion.
It should go back to Blue.
But a screen cast of your issue will certainly help diagnose the issue.
Hope this helps.
