I can't make everything work, but maaaybe you are a
Some are found through start and gates,
Microsoft Windows. (Bill Gates.)
Some are born of carbonates.
Polycarbonate plastic (not as nice as glass, but e.g. it's what the windows of my shed are made of).
Something employment likely hates,
I don't have a good explanation for this. (Maybe some employers don't like the idea of their employees sitting at their desks gazing out of the window instead of working hard?)
You'll have to reach to activate.
Opening windows high up in the wall can be something of a stretch.
Allow a star to penetrate,
Windows are transparent and you can see the sky through them.
With colour added they fascinate.
Stained glass windows?
Sometimes I'm blinded by those that can see,
Blinded = having a blind attached.
Sometimes it's hard to even see me.
Again, windows are transparent. (As birds sometimes discover to their cost.)