To get a model printed in color, first you have 3 options with Blender, diffuse material color, vertex color, and a UV texture assigned to a map.
Remember that there are only a few file formats that SW accepts color info from for Full Color Sandstone, the only material you can get color on. X3D exports from Blender work well for uploading.
If you have a UV mapping going on, before you upload select the texture and export file at the same time,compress both of them in a
single zip file. Upload the zipped file to SW.
You will have to do some scaling to your model,before uploading. For color printing a Blender unit is regarded as a meter at SW. So they will try to print the default 2x2 cube at 2 meters by 2 meters.Which is impossible for the printer.
1 workaround is to determine the printed dimensions you want. Say you want the default cube to be printed at 2cm x 2cm.Just set unit measurement in scene data to meter. (instead of just 2 for the three dimension values, it now is 2m.)Then in the N panel, replace the three dimension values with 2cm. Notice it gets scaled down. To show why it works, in scene panel now change it from Meter to None. The dimensions change to .02. each. So now when you upload the file, it gets printed at .02m cubed when you select Meter at upload. .02m=20mm=2cm. Apply scale now . CTRL A, and export. Or just scale the model by .001 and apply scale, export.
If you downloaded the model,and the texture was packed in a Blend File, it will need to be unpacked, then follow the highlighted steps.
Keith