There are several things that will determine what colour each dye produces, the most important being what you are dyeing, and how much dye you use.

Different fibres will give vastly different shades, for example animal fibres such as wool generally tend to result in richer, deeper colour than cellulose fibres such as cotton, which generally tend to be paler.  But the structure, age, whether the fibre has been scoured, and so many other factors affect the colour, and the only way to find out is to try!

The other main consideration is how much dye you use - almost always, more dye will give you darker colours, and less dye will give you paler colours.  Recipes and guidelines are generally given for a medium depth of shade.  If you would like paler colours, you can use less, if you would like darker colours, you need to use more. 

Dye amounts are calculated based on a percentage weight of fibre (wof), which means you determine how much your fibre weighs, and multiply it by the percentage given for each dyestuff.  

For example: for a 100g skein of yarn, and your wof percentage is 5, you need 5 grams of dye.

You can always dye without measuring (the joy of natural dyeing comes with the experimentation), just follow the general guideline that if a dye has a low wof percentage (i.e. cochineal, at 4-8%) you don't need very much dye, and if it's higher (i.e. madder, at 10-30%) you need more dye.

Some average, general weights of items you may be dyeing:

1 metre of medium weight woven fabric, like a quilting cotton: 140g

1 metre of medium weight knit fabric, like a cotton jersey: 200g

1 medium women's t-shirt: 100g

Skeins and balls of yarn will have their weight marked on them