How to Set Transparency to One Specific Color in EEVEE What I want is assign the black color as an alpha or transparent, then the red color as a normal shader. I'm using EEVEE. 
My render result: 

What I actually want (edited in external app) :

My node:
Oh my actually it's simple, I use wrong shader. It should be principled BSDF, not emission. So what actually to do is:
 - Set black color of color ramp to alpha. Decrease alpha value to zero should work
 - Color output of color ramp must be connected to color of Principled BSDF, and alpha output to alpha input.