Need to repaint my exterior, a couple of question with painting
If your goal is to touch up sections without a whole house painting...

In an inconspicuous area, use a razor blade and skim off a small section.  Take it to Home Depot and let them use their paint matching machine. Then have them mix an exterior paint for you.

I did this for an interior wall once and I could never tell the difference after it dried.

I would scrap and prime the bubbled portions of the wall.  

My 2 cents