Former xiaomi & poco user here.
I used to troubleshoot and fix Xiaomi and Apple devices myself, as long as it didn't require soldering.
I've noticed a common rookie mistake: jumping straight to buying replacement parts without pinpointing the root cause.
You might end up costing more if, in the end, you have to send your phone to an authorized repair center.

If your screen lights up but looks off, there's a good chance the display panel or motherboard could be the issue.
It's a pretty common problem when the screen appears that way.

Another thing to note is not taking a moment to Google the issues for your phone and the repair costs.
Everything, from parts to labor costs, is usually well documented.
https://www.mi.com/my/service/support/materialprice.html

You can always call your nearest repair center to see how much they charge for just diagnostic, if the repair cost is too high you can always reconsider.
Before diving into buying parts for a DIY fix, it's wise to compare the total repair cost, time, and effort involved, before dive into buying parts to DIY your own.