By default,the colours of your launcher and panel mimic the colour of your desktop wallpaper.I am assuming you are asking how to change that.
If you don't already have it,install the compiz settings manager using
sudo apt-get install compizconfig-settings-manager
Once installed,use the dash to launch it.
Click on the category Desktop.
Click on Ubuntu Unity Plugin.
You will see an option called panel opacity.Try changing it to a higher value.You can can then click on laucher option and increase the laucher opacity as well.higher the opacity,less the colour will resemble that of the wallpaper.I hope this answers your question.
it could also be that the resolution of the wallpaper you are trying to use isn't right.To find the resolution that will work best for your monitor,check the resolution of your default ubuntu wallpapers(you can see that under appearances).