Adzuki Beans will pale as they swell with water. Before you end your soak, check them: If you see that on a lot of your beans, part of the bean (one end usually) is still as dark as it was before soaking, they may need a little more time to soak - to make sure they have taken up all the water they need. This is difficult to explain, but I will of course try. If that dark red is no more than 20% of the seed, consider it fully soaked. The seeds continue to take up water even after soaking, so they'll be fine. If more of the seed than 20% is still dark red, drain the soak water and add fresh water. Soak for a few hours more and check them. You'll be done soaking when the seeds are at least 80% pale. Of course, if you got your seed from us, we will tell you here if you need to soak them for more than 12 hours. We haven't had a lot of Adzukis that required such special treatment since the last millenium, so don't sweat it - if you are using Sproutpeople Adzukis.
In any case, we soak Adzukis for 12 hours. If we are in a hurry we'll use warmer water - 80-90° is a good starting point if you want to experiment with shorter soak periods, but be careful not to go too hot - it can cook your seeds in which case they will never sprout.
Adzukis also tend to have more hard seed than other seed types. If you buy your seed from us this is not much of a concern, but these are beans after all, so it is always good to check for hard seeds - as well as rocks (hey, these grow on farms! Dirt Happens!). If you buy Adzuki or other seeds elsewhere be sure to examine them after soaking to make sure there are no hard seeds (seeds that are as hard after soaking as before) . If there are - throw those (the hard ones) out (or better yet, compost them)! Hard Seeds are easy to spot as they are smaller than those that are swollen with water.