Everyday we have customers walk through the door needing to match their vinyl siding. Of course color is a big deal its actually not the biggest deal.
First of all, forget the grain. Chances are you will not match a grain unless the panel is less than a couple of years old. Manufacturers change their grains often. I always tell people, when you get 5 ft away from the panel you will not notice the grain.
The size of the panel is usually the most important factor. When matching vinyl siding, one needs to measure from the bottom of the panel to the first "lap". This measurement will typically be 4, 4.5 or 5 inches. There are 2 laps, giving the appearance of 2 boards per each individual panel. This is called either a D4, D4.5 or D5 which stands for Double 4, Double 4 1/2. and so on.
Next is the style of the lap. There is a dutch lap and a straight lap. Dutch lap has a bevel in the panel and a straight lap is just as the word implies. For more examples of these profiles, please visit the Standard Vinyl Siding page