Google Sketchup is good for visualizing 2d 'casting' of 3d shapes simply and fast, but I think you
shouldn't use it for shading reference I'm almost sure that it shades faces prioritizing the differentiation between them, and not necessarily a correct light source.
(and in any case, I believe the lighting isn't modifiable anyways (direction, strength, dissipation...) so even then it would only be useful for 'high noon'-type scenes.)
Your house is shaping up nicely.
The colors you use should depend on:
1. the atmosphere of the game (darker and less saturated = spookier)
2. the rest of the scene (a background element shouldn't stand out too much, with some exceptions)
I feel as if there should be a bit more roof in the left side of the house, if you know what I mean.
Right now, it looks somewhat unbalanced to the right, to me.