Oh probably there was a little misunderstanding. I didnt mean that copy color key frame causes crash. I meant that u click on the key frame to hold position, then open slot color managment (Set slot color) and from there copy color code (FFFFFFFF). After this, go to the another skeleton (you dont have click key frame again because it is saved from lastest skeleton, that is what I meant as "to hold position"), open slot color menu and then paste color code.
When I did it with several key frames, Spine crashed.