[Idea] Last hit detection

The Problem: As someone who plays with several different champions I sometimes misjudge the amount of health a minion has and try to last hit too early causing me to lose potential gold even if I am watching the amount of damage it takes. This is especially more difficult in lanes with high pressure champions that try to prevent you from last hitting minions at every opportunity. I usually end of falling behind in CS due to not being able to determine when I can last hit minions.

The Solution: Some kind of visual mechanic (i.e slightly enlarged health bars when minion is near death) to let you know when last hitting a minion draws closer. It doesn't have to be spot on but it would definitely help me in determining whether I can last hit or not and alleviate some of the focus on the minions health and put more focus on the enemy and what they will/may do.

On a personal note, I have tried to learn to last hit minions better and have done so on some champions. I just thought about this after learning about Health Bar changes and how it would help the player to determine where they are on the map and to alleviate a lot of confusion on player placements.

Any feedback on this idea is appreciated.

EDIT: A lot of people have said already that it is a skill that you learn. While I agree, it doesn't change the fact that their health bars are really small in the first place and so for someone like me with ADD I don't notice when they are low. There is a lot guess work in last hitting and would just like to alleviate that kind of problem. While it may not be ideal to have this kind of system in place. Anything that could help practice with last hitting or changes in the minions health bar as deathbunny82 mentioned with segmented bars would be a godsend for me.