Oh, so you're creating the "hippy" designation as a throwback to the Woodstock/Free Love era vibe apparently associated with Green/Low Power/Environmentally Friendly drives? If so, got it.
No, you can't crossflash. Otherwise folks would buy green drives and flash them into 10k rpm Raptors. And it'd still be helpful if you would specify manufacturer/model #'s so folks can get specific in their comments.
As far as I know, Green drives most certainly do not have the same spindle speeds as the "standard" drives. Green drives typically spin at 5400-5900 rpm, and standard drives typically spin at 7200 rpm. High Performance drives spin at 10k rpm. I use LP drives in my NAS because I don't care about blazing random access since my data is typically accessed sequentially by 1 user at a time. I value the NAS being quieter and using less power (since it's always on). If one needs simultaneous random access (such as databases), the "standard" or even "performance" drives might be more desirable.