What do you mean by color? A image texture or a simple color?
If it’s a color then you’ll have to manually set the color in studio easy task
But probably I think you got multiple colors in one model and you might have exported them all in one .obj file
If you want to be able to color parts of your model you’ll have to separate and export each objects and color them in studio.
Another solution would be making a uv map and creating a texture with the colors you want and import the image in studio but that’s very ineffective and not recommended.