I disagree Fighting_Scars (and welcome to the Chaos area! =D). While that purple, yellow and flourescent green does sound cool, I have seen some great pink armies that look awesome. Remember that on the color arc, pink stretches towards gray, and so a light pink can be really eerie next to black.
If you make a Slaaneshi army, you are not limited to the sexually interesting pinks and purples. I think that any combination of stark color contrasts (that look good) or eerie combinations would prove to please the Lord of Pleasure and Pain.
The coolest look on the new Emperor's Children miniatures that I have seen is a pale yellow contrasted against a bright, bright green. It's very off-setting, but then strangely intriguing once you start to look at it. Perfect for Slaanesh.
I do, however, agree with Fighting_Scars that including some Chaos Space Marines would be a good bet. They're always reliable and can provide some good firepower to supplement your Noise Marines. Also, as a heads up, rumor has it that some of the Noise Marine weapons will change in the new Codex...at least some of their stat lines.