plonisalmonis, thanks for explaining. It’s seems that your parents feel that you are criticizing their tznius standards, so it may be best if you avoid discussing this issue with them. Perhaps it would be best if you try to anticipate when you will be asked to go outside to help–say, if you know that someone is going grocery shopping– and put on tights before that. You could even throw out the garbage without being asked, if this is possible, or go outside to help with the groceries as soon as the shopper returns home. That way your eagerness/ willingness to help would not be questioned.
If you are asked to go outside unexpectedly, and need to put on tights, it may be best if you do not frame the issue as a tznius one, but instead say, “I’m more comfortable wearing tights”.