This method takes advantage of the material layer Valve uses to spice up images you send to them. Valve put in a file that goes over whatever image you send them, and you simply load a replacement with your target image in place of it.This image when fully opaque goes over whatever image you load, making it perfect to bypass the funky colorization scheme.

First go to your main Steam window, and click on Library. Find Team Fortress 2 in your list, and right click it. From the pulldown menu, select Properties.

From here a window pops up, click on the Local Files tab, and then click "Browse Local Files..."

From step one, double click the /tf/ folder, then the /custom/ folder. If it does not exist, create it.
Inside the /custom/ folder you should create a new folder and name it whatever will help you remember that this is for full color flair/objectors.
For example, let's say I name my folder "PEBKAC", once I open it I should be in
Inside that folder you create the folder named "scripts".
Inside /scripts/ you create the folder named "items"
Inside /items/ you create the folder named "custom_texture_blend_layers"
We're now at

Go to Step Three
Go to Step Four

Inside the last folder you created, custom_texture_blend_layers you need to save your image as a 128x128 pixel png image with the name "paper_overlay". After you've put it there, start or restart tf2, then start the process of applying your decal to an objector.
You can pick any image, I usually just use my avatar. Click the Next button. If you've done it correctly your image will show up.If your image shows up like mine did, it's time to finish the application.

Inside the last folder you created, custom_texture_blend_layers you need to save your target image as a 128x128 pixel png image with the name "flair_template_guide". After you've put it there, start or restart tf2, then start the process of applying your decal to the Flair!.

You can pick any image, I usually just use my avatar, but for Flair! it works better if you have a fully white image to load. Click the next button. If you've done it correctly your image will show up.

Adjust the gradient slider until whatever image you picked isn't interfering with the image you put in the flair_template_guide.
If your image shows up like mine did, it's time to finish the application.