Second that! What a pain!
I hate Rustoleum rattle cans, but they have a blue that is a dead match for old Bahama Blue. I use pinked edge masking tape for repairs, and it just looks like surface tape edges. Maybe I will get you a picture.
Off-white is a bit tougher, but we have matched old Juneau White with rattle cans. Let me see if I can identify the color/brand. New Randolph Juneau has a yellow cast - the older good stuff was Insignia white with a hint of black.
Rustoleum used to be pretty good. For the last decade or so, their cans are good for about a month, and if you do not use it all up by then it will clog, and it won't be just the nozzle. Bad for the environment. I now use DupliColor when the colors match.
A quarter century ago, Randolph was the very best! They moved it west and changed all the colors, and cheapened the pigments. Opinion.
Edit - just saw Ed's post. Scoutdog has it about right - proceed with caution. Insignia White is still a pure white, and is rarely used as a base color. Most use Juneau white, but I do not care for the newer color - looks like a used bedsheet.