A long time ago, I began marking the positive lead of all of 
my equipment. At first I did this by wrapping a twist tie 
around it. Now, I use a small zip tie that is pulled tight 
around the lead an inch or two behind the ring terminal or 
whatever is on the end of it, and then cut off as close to 
the fastener as possible. This gives me an easy tactile 
indication of the positive lead should it be necessary to 
remove or re-attach it when there are no working eyes 
around.

By only marking the positive lead on each power cable, you 
know which lead is in your hand when your at the power 
supply end of the cable.

Every ham, blind or not, should do this.

Mike Duke, K5XU
American Council of Blind Radio Amateurs