In order to help you I've found a chart that shows you all the instruments and their frequencies.
It tells you exactly what frequency muds your intrument or brighten it for example, only by just mouse-overing onto it!
It's so useful especially for beginners!
Do not use this chart just because you have it though.
hen you master the sweep technique you won't need charts and mixing according to charts blindly won't help you improve your mix style...
And most important it won't help you train your ears.
Here is the chart though. I hope you will use it wisely.
http://www.independentrecording.net/irn/resources/freqchart/main_display.htm