The color tones of the rune basically tells you what way it is. Which is not intuitive at all at the moment, because there is only one rune of each of four different ways, so you have nothing similar to compare them to.
For example, the Dark Way runes all have a black icon with a red glow, like the Weakness rune currently available. The names are a hint also - using the Dark Way as an example again, it is the domain of death and evil, so Weakness which doesnt really fit into the Good/ Air/ Fire/ Water/ Earth ways and domains but does fit well into a domain of Evil is probably going to be Dark Way.
If your skill is at zero in a Way, you need to buy enough training in the Way to get all of the Yellow skill bar turned to Green ( the same point at which you can then get experience in mining, or using a sword ) before you are able to cast spells associated with that Way.
The effectiveness of the spell like anything else goes up as you get more skilled in the Way. With zero skill you will be able to practice it enough to get to a skill of 1, provided you have enough initial training.
