Per-cell border colors in a highcharts heat map
<p>I'm using highcharts to create a simple heatmap, but now I want to use custom border colors on the cells to represent another dimension in my data set. I am able to accomplish this with the <code>borderColor</code> config option on the data points, but the border of each cell gets drawn partly on top of the border of the preceding cells, so it looks sort of goofy. </p>

<p>Is there a way to specify a margin for the border so that my border gets drawn completely inside the boundary of the cell, so that there is no overlapping of borders? Or is there a way to custom-draw my own border through some event?</p>

<p>You can see this effect in the fiddle at <a href="http://jsfiddle.net/8ft7e923/1/" rel="nofollow noreferrer">http://jsfiddle.net/8ft7e923/1/</a> and in the image below. Note how the orange border is drawn over the green and the red is drawn over the orange. This overlapping is what I am trying to eliminate.</p>

<p><a href="https://i.stack.imgur.com/lf6gG.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lf6gG.png" alt="enter image description here"></a></p>