I doubt the blue is for left and light green for right. If you've got RCA jacks for audio, white will be the left channel, and red will be the right. Computer audio connectors usually follow this color code (copied from Wikipedia):
green TRS 3.5mm stereo output, front channels
black TRS 3.5mm stereo output, rear channels
grey TRS 3.5mm stereo output, side channels
gold TRS 3.5mm dual output, center and subwoofer
blue TRS 3.5mm stereo input, line level
pink TRS 3.5mm mono microphone input
The blue indicates an input so connecting speakers to it probably won't work well. I suggest you use the green jack.