Wrong Values when importing Node

Hello forum.

I made a Node Group with sub NodeGroups and Append/Link it in another blend file.
The problem is unconnected color inputs are pretty random. Some black, some white.
This is an issue for me because all unconnected color inputs which are not set to black with zero alpha, the result of my node group is black.

I tried to set these default values but they stay at the same colors.

Is there a way to fix this, or is it an unpredicted case/bug.