Hi Mandi. As a designer who does staging consults for resale and has just gotten into flipping myself I would like to field this one for you because it is much more complicated than just color choice. I disagree with your contractor that "as an investor it's not smart to go with blue". Blanket statements should never be made about real estate, design, or life in general for that matter. It truly depends on your market! There have been some highly unscientific "studies" that show that blue houses sell for less, but these did not analyze individual markets, architectural style or appeal of varying shades of blue. Additionally, architectural and decorative features of the home usually figure heavily into whether or not blue is acceptable and should be considered as well.
To illustrate take a look at these these stunners below:
I don't think anyone would disagree that these are all highly marketable properties and they are all done in various shades of blue. The first is a Coastal home, second Tudor and third Craftsman cottage. Notice that white was chosen as a trim for each of these which sharpens the look and breaks up the color, and there is significant architectural and design detail that makes these homes interesting.
Now, look at these homes:
Not horrible, but an old metal awning and iron railings on the porch and no architectural detail make this blue house less appealing. Notice the color of the house is not the problem here. A new portico and craftsman columns on this porch would really boost the curb appeal, as would some plantings to soften the look of the foundation.
Again, you can see the color is not the problem with this house. An overgrown bush, yard ornaments and odd bicolor door and trim add to the lack of appeal here. The two siding orientations don't help either. I would change the siding where it was hung vertically to something more eye catching like shakes or board and batten, add some beefier white trim around the window and door, paint the front door black and clear out that front yard. Voila! Cute blue cottage.
I think you picked a beautiful blue, but if you are feeling uneasy about it, analyze the other details of the facade to make sure the color isn't falling flat. You don't have to spend a mint! Often it's small changes that make the most difference. I hope this helps and good luck. Let me know if you need any clarification.