Will 38 special ammo fit in a 38 colt revolver?

Maybe.

You need to figure out which .38 your Colt is chambered in. .38 Short Colt and .38 Long Colt guns will not chamber a .38 Special. .38 Colt Special is the same as regular .38 Special.

If you cannot tell which caliber it is you need to take it to a gunsmith and have him tell you.