There is no mod for this but it can be done if you do mod a config file yourself.
c:\Games\World_of_Tanks_EU\res\scripts_config.xml
Decode it with wottools 0.5.2.exe and you should receive something like this:
You need to change values in this <silhouetteColors>, they're represented by RGBA
the enemy outline color is in this:
<enemy>1.0 0.070 0.027 1</enemy>
1.0 = R
0.070 = G
0.027 = B
1 = A (alpha / transparency)
and this (for CB):
<enemy>0.511 0.472 0.992 1</enemy>
When you finish, place that file it res_mods/0.9.21.0.1/
Finding correct values:
1.) get the hex/rgb color code of the target color, ie.:80d63a
2.) go to http://www.colorhexa.com/ and put the hex color code in the box, press enter
3.) go down to "RGB Percent"
4.) divide the values by 100 and round to one digit after the coma. for the example this would be 50.2, 83.9, 22.7 = 0.5, 0.8, 0.2