About locomotive paint, Google Pantone, who makes a color matching chart with about 1300 color shades. Find a match and look for the color number. You can also Google "Pantone color chart" then click "images" but differences in monitor color resolution can make a match inaccurate. Brand new color guides are expensive and are designed for professional graphic artists, but used ones can be found much cheaper on eBay.
Next, try 1Shot paint, which is commonly available at art supply stores (such as Blick Art Supply). Their web site has a color matching formula page where all you have to do is type in the Pantone color number and it gives you the exact mix of paints that you'll need. It's really handy for more than just the Alaska Railroad. I found a match for Atlantic Coast Line purple used by Atlas Model Railroad Company using this system.
1Shot is great for those of us still addicted to using lacquer based paints. It's also much cheaper than Floquil used to be.
Tru Color does make an Alaska Railroad blue, but based on the color chip on their web site I thought it was too light for current Alaska Railroad locos.