Suppose you want to draw a white text using a texture on a blue QUAD rectangle.
We tryed making a white text on transparent background image and using the blue color for the QUAD object but the white color was affected by the blue one.
Then we tryed making an image with the white text on a blue backgroud and drawing the QUAD with white color, the result is better but the blue color is not reflecting light exaclty as all the other (non textured) QUAD with the same RGB color.
What is the best apprach to achieve a perfect result?
Well, you can use GIMP or Photoshop, see the different blending modes - and pick the one you like. Or code a shader to draw the text on blue background (blending disabled), but with some custom color-blending in the code.
but honestly, it is much easier to do it in two passes.
First pass:
Render blue quad as usual
Second pass
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
Render white quad with alpha transparency texture.
glDisable(GL_BLEND);