Imported OBJ file with transparent texture has black background When I import OBJ file with texture image of transparent png and red background I can see the color of red is correct when in Solid Preview mode.
But once I switch to material or rendered preview mode where I would expect to see the image with red bg all I see is the image with pitch black bg - why?
In fact I am just testing if the OBJ file is OK (it is OBJ I made, generated by the Blender 2.8), cos it does not show texture in UE4 where I want to use it (so now I know the info about the texture is correct and something else is wrong with the UE4, but that is another topic, of course).
PS: I would like to have a solution without using of NODES, if possible.
Edit : So my answer only answers partially to your problem, whoever knows a bit better about Obj and Mtl imports will hopefully give you a better answer.
I don't know how to work without nodes, so I show you the problem and the solution with the nodes:

You want your arrow to show up on your object on a red background, here is the current node organization:



This node organization doesn't allow you to show any background, so it shows only black where there's the alpha transparency. The red you see in Solid mode is actually the color you've picked as Viewport Display color:



To create a red background, you have several solutions, you can plug your Image Texure into a MixRGB, choose a red color in the second socket, and plug the Image Texture alpha output into the factor of the MixRGB: