Want to make negative X axis values a different color

I'm trying to create a bar chart which has both positive and negative X-axis values (X-axis values range from -15 to +20). I see how you can invert the colors of the bars depending on whether the Y values is negative, but I cannot find how to do this when the X value is negative. The scenario here is I'm charting the frequency of arrival times relative to a fixed time (zero) so negative values are early and positive values are late. I'd like to color the columns that are late a different color so they stand out. I'm using Excel 2010

Not sure how to upload data on here. But column 1 has numbers from 15 to -20 (this would be X value in chart) representing the time relative to the zero mark. Column 2 has the number of times each case was observed. One example is where column 2 has 1 in 15, 1 in 4, 2 in -1, 1 in -5, 1 in -8, 1 in -9, 1 in -13, 1 in -15, 1 in -18, and 1 in -20. So I've created a nice little bar chart showing the distribution, but I just want to highlight the positive bars (which represent arriving late).

So yes, I can double these columns and just replace zeros for the above/below zero marks to get two data sets and change the colors of each. But I have dozens of columns already, so doubling them and recalculating each would be a significant effort. I was just hoping there might be another easier way to do it like the "invert colors" button that only applies to the Y axis.

Yes that chart is what I had in mind, but it looks like there's 3 times as many columns of data as I started with :/