I don't believe it's possible to apply a colour to numbers in a chart data table.
However, I may have a workaround for you that means you can use a formatted table stored on a different worksheet, so that it won't affect the existing row and column heights on your worksheet. It's a bit of a hack, but will get the job done.
Use Excel's Camera Tool
To use the Camera tool, you need to customise your toolbars.
In Excel 2010 you can add it to your Quick Access Toolbar:
Create a new worksheet and create your table with your conditional formatting as you want it laid out. Then select the entire table and click the camera tool button. Go to your chart, and click just below the chart where you want the table to appear.
You should get something like this. Don't worry, we're not finished :)
We have three problems to address here: the width isn't right, the text is a bit grainy and there's a border we don't want.
First let's deal with the grainy text. I've recently faced this problem and worked out how to deal with it. Firstly let's delete the image you've got - we need a fresh image, then go back to your table on the new tab.
Now select your formatted table but this time with around 20 blank rows below your table. Select the Camera tool again and click below your chart. Now, right-click and crop your image to only show the data you want.
Removing the border is easy - right-click the image, select
Format Picture and set
Now you should have something like this.
Finally we need to sort the width out. You can either mathematically calculate the widths you need to use, or just a bit of trial and error. Select the columns containing your table and widen the columns a bit.
Go back to your camera tool image and the text will look squashed. We need to adjust the width of the image. Right-click,
Format picture then set the
Scale width to be the same as
Scale height (because you've changed the width). Repeat until you've got the width as you want it, something like this:
What makes the Camera Tool so Great?
The wonderful thing about the camera image is that it's not static - if your data changes, the camera image will also change, automatically. It's a great tool!