I admit I'm quite fond of the greyed colors too. They have a 'vintage' feel that I adore.

The foreground on the dyke is really interesting - lots of colors on the ground - fallen leaves maybe? I imagine that the blue on the rocks may be frost or ice. It really gives the painting a 'living' feel. I expect that he created a more animated feel in all of his art though. The fountain is only a sketch but seeing the photo next to it... Your grandfather's drawing looks much more interesting. I love how he saw these places.