I’m a bit lost in real life there is a tint on the outside so you cant see inside but on the inside you can see out when I do the windows it does both sides so you can’t see out of them at all, also it keeps painting the handrails black for some reason
The reason you can't see into the bus through the tinted windows, but can see out, is because it's (usually) lighter outside of the bus than it is inside. The 'extra' light coming in from outside makes the tint look like it's not there from within, while the lack of light inside the bus interior emphasises the darkness of the tint and makes it hard to see in from outside. Even on buses without tinted glass it's harder to see in than look out.
The reverse is true at night, when the bus interior is lit more brightly than outside. It's easier to look in at the bright interior from the outside than it is to look into the darkness from inside the bus.
Unlike real life, OMSI's lighting physics are much more even (harsh shadows don't really exist in the game), making the lighting environment both inside and outside the bus pretty much equal. So the window tint is equally visible when looking from the inside out or the outside in.
So it's not a problem with the bus or your repaint, it's OMSI's simple lighting system being untrue to real life.