So,  I have a colorless demon's soul - which I gather are pretty hard to get and I want to use it wisely. My two weapons for most of the game have been a winged spear +7, and the Magic Sword Makoto. So I'm thinking I'll use it to upgrade Makoto, but also was thinking maybe my Adjudicator shield which I use from time to time.  
Another question I have is about weapons in general. I see the Makoto sword has really high damage and causes a lot of bleeding. But I don't hear many people talking about it as a good weapon. Is this just because it is harder to upgrade, and also doesn't have any stat bonuses? Should I be putting more time into upgrading a different sword instead? I definitely prefer a quicker sword. Current stats are: Vit: 27,  Int: 17, End: 26, Str: 26, Dex: 20, Mag: 17, Faith: 12, Luck: 11 
Any suggestions?

You can use this site to decide whether or not the upgrades are worth it. It says that Makoto is a good starter sword but becomes weak later. I haven't tried it as I usually go for the big weapons such as Crushing Great Axe and Dragon Bone Smasher.

personally i almost exclusively use blueblood, so i haven't actually bothered using colorless souls.  
 
mokoto isn't worth investing in if you ask me. my guess would be hiltless is better if you're looking for a katana type weapon. additionally, spear are pretty much useless outside world 2.

1. Change the world's tendency into black. once you get the world near to black tendency only then a primeval demons appear and after you kill him you get a colorless soul. Each world has one primeval demon but don't worry though. They are very, very easy to kill. 
2. There's a colorless on world 1-1 on a beam below the area where you kill Miralda the Executioner. It's the area after that locked gate in the beginning of the level (to your left). The gate will open up only once you got the world tendency to white. Killing at least 3 bosses in world 1 should take care of that. If you say you only have one colorless then I am guessing that's the way you got it. 
3. The third and final way is by doing the quests Mephistophele gives you.

The 4th way is to exploit the crow duping glitch to get infinite colorless souls. Check out the farming page over at the DS WIki:
 
http://demonssouls.wikidot.com/colorless-soul     
 
EDIT: Also, don't use Makoto, there are much better options especially as your soul level increases and yes you are right that's bc it has no stat bonuses.