Your aunt is havig a complication this is unfortunately a potential complication of cardiac cath.
It is usually self-limited and appears ugly will almost always have no long-term consequences. According to my hosptial discharge information it states "if you notice numbness, pain, redness, infection or increasing size of the area you should notify your doctor. It may take several weeks for this to completely disappear". I agree with flycaster if there is an infection there should be a fever, and don't delay in seeing your doctor..
Hope this helps, and thanks for your question. If you have any followup questions you are welcome to respond. Take care and I hope your aunt does well going forward.
The thing is that you need to let the doc know...the things you look out for is red....hot to the touch and swollen......it is normal for the bruising to be there even if it is red inside of the bruises.....i don't understand what the coldness could mean ...it could be something or nothing...best not to take a chance and call her doc tomorrow just to make sure....
A bruise after an angioplasty is very normal. I would urge your aunt to get it checked, however, if she has any worries about infection.