There is no definitive way to be sure. Red photographs as black on orthochromatic film (by far the most prevalent type of film used during the Great War) and so, without some sort of corroborating or supporting evidence, it is most times impossible to say
for sure whether red or black was the actual colour.
When the red and black decals for this particular Albatros were designed, it seemed that the balance of opinion favoured that colour configuration. By the time Greg VanWyngarden's carefully researched Osprey book on Jasta 18 was published (some years later), the black and white band option was thought more likely and so I went with that in the dedicated Jasta 18 set.
If you think that red and black was more likely or that it looks "cooler" then use that combination on your model and challenge someone to prove you wrong! They won't be able to, only to offer a balance of probability that, as the bands were in the same proportions as the stripes on the Prussian Iron Cross medal ribbon, then the black and white of that was probably (
probably) the inspiration for that aircraft's fuselage bands. Many other Geman fighters carried the same proportion bands for just this reason.
Incidentally, I've also recently changed the black diamonds on a Jasta 17 Albatros in an earlier set of decals to red in the new Jasta 17 set, due to new information appearing in the recent Osprey Jasta 17 book. These things will continue to happen as the depth of our knowledge increases.
So please don't look for absolute certainties from me on all colours; I'm as much a victim of colour interpretation as the next guy. I do virtually no original research (using mostly published sources which are credited and listed in each of our decal set booklets) and I am largely reliant on others who do all the hard work of researching from primary sources, occasionally supplemented by my own interpretation of images and evidence. Buy one of our sets, if you like and you'll see. If you are particularly interested in Jasta 18, then I suggest the dedicated set 72016 will provide you with lots of different markings, and a wealth of background and colour information.
http://www.pheondecals.com/72016-jasta-18-vol2-ldquorabenrsquos-ravensrdquo.html
