Hello jm22 --welcome to the forum...... you`re in the best place to have your hair loss sorted with top- quality systems at down -to -earth prices.
The link that Anthony posted is well worth looking through... there is a colour chart there from which you can pick your colour [ for some reason that particular part of the page will not open for me ] but the ultimate way to get a proper colour match is submit a sample of your own hair if possible, about the diameter of a pencil. That will be sent to the factory,along with your template for a match.
As regards blending/shortness of the cut ......... what length is your side / back hair and is it still dense ? If it`s cropped tight in to the head, probably best to leave it grow a bit longer... this will help with blending the system hair onto your own ..... maybe you could post a pic so people can chip in with their advice ? Regards, Paul.