Transparent cables are typically directional. The red marking usually indicates the destination end, meaning it should be plugged into the component receiving the signal. So, in your case, the red end should go into your DAC or whatever device is receiving the digital signal.
If you want to confirm, Transparent often designed their cables with signal flow in mind, meaning the text on the cable should read left to right in the direction of the signal flow (from the source to the DAC).