dcrobot's prototypes use a different color border depending on the tile: http://5ejbb7.axshare.com/enhanced_view_-_concept_1.html We could probably do some color detection near the edges.. perhaps take an average and use the appropriate border color?

Is this still the direction we want to take for border colours?

Any tiles with a white (or very light gray) background will have a blue border. Any tiles with any other color – or an image – should have a white border. Both produce a blue glow. Does this clarify?