Well it works, it does change colors for a second or so but it is not long enough for me to notice it.

Is there a way to make it be animated for longer or another method of alerting me about new messages?

One option would be to enable tray tips from mIRC's options for new messages. This will pop up a tooltip to make you aware of any new messages you receive. There are a variety of options available. Alt-O > Display > Options > Tips.

It works but it appears on the right, is there a way for it to appear in the left side?

You could create custom tips using picwins, so you can place them wherever you want

As mentioned, you can customize an option, but the normal tooltips are only available on the right. If that doesn't work for you, you can use other methods, such as enabling a sound when a message is received. Custom sounds (WAV, MID, or MP3 files) can be used so you can make it noticeable without being annoying.

Whats picwin? How do I download it? Welp

.: Picwin is Picture Window. Custom window created by mIRC scripting language. :.

Maybe you should just get used to looking at the bottom right of your screen. FWIW, mIRC puts these notifications in the standard location that every application uses for such tray tips, so you should be used to looking there for notices.

I don't know any applications that use the bottom left corner of the screen for notifications.