If you’re like me, you frequently have many environments open at the same time in putty, sqlcl, sqldeveloper, or other tools. This happened quite a few years back, I was switching between my dev, test, and production environments, doing some work, then the “Oh S^#t” happened. I shutdown production when I thought I was in dev.
You can change your prompt to show what environment you are working in; yea’ that works … but I’ve taken this a couple steps further. Out of habit, if I’m not actively doing work in production, I close it. Second, I changed to colors of my screens to tell me what environment I’m in at a glance. Test is green, dev is blue and production is RED.
This way, if I’m about to do any work in production a cold sweat breaks out and I ask myself, do I really want to do that? You can do this in putty, and sqlcl.
In sqlcl (on windows), bring up the property dialog, click on the color tab, and select your foreground 
and background colors. Then click OK.
In putty, bring up the configuration dialog. Load the configuration for the environment, click on color under the Window tree, select default foreground, then modify button and 
select your foreground color. Then select default background, then modify button and select your background color. Go back to session tree and click save.
There you have it, this will make things a lot safer when you have multiple environments open.
I recommend closing your production connection if you are not actively using it. You can’t be too safe.