There are valid points to both sides, although the one that stands out for me seems to be that it still takes a given amount of whatever to produce a given amount of electricity.
If the source is more nuclear at one point in time while being more coal at another, then depending on exactly how you define 'green', the answer could be yes or no.
If one only refers to carbon emissions, then yes, using the power when nuclear has a higher standing would be 'greener'.
However referring to overall impact, I would have to say no. You still have to use the nuclear fuel, and ultimately must dispose of it somewhere.
Until RE takes a much stronger hold, this line will remain a rather blurry definition, and will provide hour upon hour of heated debate, I'm sure.
The only way to get greener in the latter of the above, is to reduce (and eventually eliminate) "stored" energy (ie. fossil, nuclear).
We will have to wait and see, I suppose...
Steve
