I visited that website you provided, and it's a bit confusing to me too, but I managed to find the "Foundation" page. There's actually a few different type of foundation depending on their cover and finish, but I think "IT" has the best coverage out of all.
http://www.beautychamber.co.uk/everyday-minerals-foundation-base-p-1863.html
Now, the thing about mineral powder is that it's hard to find a perfect match for your skin tone... But since you said u want to be darker, then I guess the color "Golden Medium" would be the best to try out~
And you will need a brush for applying mineral powder
http://www.beautychamber.co.uk/everyday-minerals-long-handled-kabuki-p-1823.html
^This one is exactly what I used for applying everyday mineral powder.
From my experience with make up, mineral powder is very good at evening out skin tone and neutralizing redness. Though the coverage is somewhere from light ~ medium.
If you really have noticeable redness, then u would need a liquid foundation to cover it up. Revlon Colorstay Whipped is my favorite medium~full coverage foundation.
And remember, the BIGGEST tip I always give out to people about make up is that, ALWAYS use a primer before applying any type of foundation. Primer helps the foundation to stay put and last longer and look better.
Smashbox primer is a good one.
If you get breakouts from using cosmetic products then I would not recommend mineral makeup as lots of people report breakouts from it.
If redness is your only concern and you don't want full coverage for severe acne then I wouldn't suggest anything full coverage as it will be more detectable.
Mineral Foundation also tends to give a bit of a shimmery glow when in direct sunlight so it's not most suitable for a man.
I would suggest you get an anti-redness (green) primer and then follow up with a non comedogenic liquid foundation which has a matte finish if your oily, or natural finish if you have dry skin. Stay away from anything with a satin finish or anything with the words "radiant" or "dewy".
I would recommend Revlon Colorstay (liquid not whipped) mixed 80/20 with a non comedogenic mattifying moisturiser. Apply it with a brush such as a Real Techniques expert face brush and really buff it and blend it into the skin. Then follow up with a translucent setting powder such as Rimmel Stay matte powder or MAC Blot powder.
Alternatively you could just use a green concealer on the red areas with a really light layer of the foundation stippled over it, as long as you don't use a drying concealer. Try to find a liquid green concealer such as the one from Clinique Blemish Solutions.
If you want to make sure any makeup you buy is the exact match for your skin then test it on your face in the store on your cheek bone.
If you'd rather not go into a store to buy it because you don't want people to see then you could buy a shade of foundation that you think will be too light and one that looks too dark and then mix them yourself at home before each application to develop the perfect shade.
Hope this helps.