Your 'blue' screws are the only screws holding the stock on. I learned how hard adding such a stock was. My SAR-1 came with a synthetic stock that I didn't like, and tossed in the wood stock for free. I decided to wait until September for a folding stock. To fully seat the wooden stock, I inserted the wooden stock as far as possible by hand, then slammed it against a concrete pad a few times. Worked like a charm!
I don't want to imagine how hard it will be to remove it come September. I'm thinking of having two people pulling in opposite directions, or using a very heavy vise. For future wooden stocks, I'm probably going to shave off a bit of wood. If she rattles, one can always put in a bit of dampening material to keep it quiet.
I suspect it's glued in place or the wood has expanded a bit. Bashing it, within reason, would probably loosen it up.