What is the color format and resolution for a design file?

What is the color format and resolution for a design file?

The required format for a design file is RGB. 
Notes
Please note that CMYK is not supported.

Furthermore, the design files for all apparels should be uploaded as PNG and JPEG for Accessories.
The system supports a maximum file size of 15MB and a maximum design dimension of 5000px x 5000px.