Can soil color give accurate data about properties which affect it?
Unfortunately, the color itself won't give you much more information than the amount of organic matter and oxides/hydroxides. The amount of carbonate and some silicates might also be detected, but those values would be very vague without further examination of the soil.

If you want to get more information you would need some more data. The grain sizes for example (sand, clay, silt), pH-measurements, the amount of water and air, what other minerals and the salinity. You also need information about the soil biota, and so on. To collect all these data you need further research methods.
So your project idea is nice, but a picture alone won't bring you much information since the soil's properties are too complex.

Also writing such a program (I guess a mobile app?) will be hard since all cameras take different pictures under different lighting.. furthermore they all have a different processing of the pictures.
I'm not sure how computer vision could help since you'd need a special camera. So if you want to make an app you're going to have a hard time. I don't think you want to design a special device just for this.

Another aspect is that whenever you work with soil, you're going to get dirty. That's no good environment for such technology, that's why the munsell charts are used. It's no problem when they get dirty. 

I really like the idea, but I don't think it'll get you far, but that's just my opinion!