Hey there, reijin2409!
I think the other way around would be a much better setup. WD Blue HDDs are good boot drives, rather than the WD Green.
If I were you I'd RAID 2 WD Greens and leave 1 WD Blue as an OS drive. The intellipower on the Green drives varies the RPM and it can cause lags as a boot drive, while the Blues are a reliable and solid solution - they are even preferred as boot drives.
Though you should keep in mind that we have specific drives for RAID and NAS systems - the WD Reds. Here you can read more about the differences:
http://products.wdc.com/support/kb.ashx?id=l9w8an
And here you should check the support we provide for desktop drives in RAID environments:
http://products.wdc.com/support/kb.ashx?id=lK9XAl
Hope...