Problem:

I would like to be able to identify genera of fungi based on the shape, size, and color of spores. So the requirements are:
Must be able to view a 5 micrometre object clearly with reasonable resolution
Must be true color
Must facilitate the measurement of an object within reasonable accuracy (500 nanometres would be nice)
Should be inexpensive ($100-$400) fingers crossed
Bonus: Be able to take photos

Required:

Question 1: What type of microscope do I need?

Question 2: What magnification/resolution? Is there a good rule of thumb relating size of object with magnification?

Question 3: How do I find and purchase a decent microscope after defining my requirements? Any tips?

Question 4: Blue light is ~450 nm, so does that mean I will not get very good resolution?

Please describe all the answers in detail.