Fixed. So it was right under my nose the whole time.
Basically within my mods folder (as each file and structure is exactly the same as in the main game's dictionary for overwriting any data I seek. The Tech Tree background art color tint is defined under (Core/ColorDefs.xml). The images are defined under (Screens/MenuArtDefines.xml)
What is very strange, is if I define the color tint under MenuArtDefines.xml under line 395ColorDefine>DarkOrange</ColorDefine lets say "Red" as the tag is defined in ColorDefs.xml, the game will ignore that command. It might be a bug hidden deep in the code that is hard coded. But a work around for this is to change every defined Tech Tree backround art color under the ColorDefs.xml alone, that will be DarkOrange, DarkGreen, DarkRed, DarkCyan, changing the color value's to "225". Ex.
So by doing this, all the backround art for the tech tree will be clear and very easy on the eyes. Now how do you swap an image?
Under the Gfx/Events folder, the following files are defined as such...
Colonizing_Event_High-GAnimalRacing.dds - Engineering Tech background art.
Event_Colonization.dds - Colonization Tech background art.
Event_Diplomacy.dds - Culture Tech background art.
Galaxtic_Event_Debris.dds - Warfare Tech background art.
Defining the image under this code found in (Screens/MenuArtDefines.xml); Texture>Event_Diplomacy.png</Texture will not change the image. Whats strange is the image type is .dds but under the code it is defined as .png, probably something im missing. So how do we go about changing it without writing code?
(Remember the folder structure under MyDocuments/GC3Crusade/Mods/YourModFolder and file names MUST match exactly as within the game's original instillation for the game to overwrite any data you need)
Assuming you have your mods folder ready to go with (Screens/MenuArtDefines.xml) and (Core/ColorDefs.xml) with the image files and Gfx/Events folders that houses the background images (see orange .dds names as above for the tech BG files)...
You need to open each file up within your image editing program that opens .dds files (GIMP is free and you can find the .dds file support online too).
Once you opened the stock image, you need to drag over a downloaded image of your choice onto the image editing program's image area, that way it will be layered on, you may need to also merge down to overwrite as one layer. After that, simply overwrite the save file.
If all is done correctly, the new image will be applied and be clear if you defined the colors that are tagged for these images up to 225 of red,blue, and green.