Onboard and PCIe sound card Qns

I have this Acer E500 a old computer.I will be using it till i have $ to build a new computer.But recently theres some IT sales and i saw some 5:1 speakers at discounted prices.But i was told I need to have 3 3.5mm jack to plug it into my computer or I could only use 2 speakers...and a sound card was needed.But when i saw the sound card. I saw several different coloured jack when I thought it will be all green.My Computer also have 6 jack with other colours.So my question is what are these other colours for, grey,Black,Blue and orange.I know green is audio and Red is mike so please tell me thanks.Sorry if my english was bad.