How large of an area are you planning on painting?
In some cases with some paints, I have seen where two cars painted with the same paint, but different primers, ie: white primer on one, black the other, the paint color has looked a bit different between the two, but it was only a slight difference, and if you are only painting a small area, you should be fine.
If you are painting an entire fender.....the primer won't make or break you on color matching. I'll admit I'm not familiar with the site mentioned above nor have I used it's products, but past experience has shown that paint in a touchup bottle or rattle can "off the shelf" just won't match.
Some members here have had success ordering a custom made color matched paint in a spray can that they purchased for less than $20 a can from an autobody supply shop. It's a bit pricey sure, but should match better than off the shelf stuff.