Re: Light Mid Colours And Darks
First you need to learn the terms. I think your asking about Values.
Make yourself a value scale; White being 1, Black being 10, and mix all of the "grey's" so that they fit evenly between.
The values you use will really depend on the situation.
In a landscape for example anything above an 8, color won't read well.
For a Graffiti piece you could use only 1 and 10 for maximum contrast.
Id suggest doing some studies monochromatically (one color) to better understand your values. Most artist say value is the single most important thing.
Buddha suggests to those who need inspiration for their art to go before a perfectly blank wall until it's design, compostion, and subject reveal itself. -Jack Rutherford