typically if you like doing housekeeping every 6 months on average.. though i've had loops running using same liquid for more than a couple years no issues.. the rig in my previous post before i moved the components into the UMX4 case, was in a 750D, and the loop was still fine after 5 years.
You won't get any leeching like you would with soft tubes etc.
Plus if you did go with colour, it won't be maintenance free since they will eventually clog up your waterblocks (not end of world, flush, clean blocks with toothbrush, reloop).
6 months would be fine. Every 3 months too much? As distilled water is so cheap. The thing that is most impressive in the loop is the fancy drain port. Lobe how it slides back and forty with a click rather than using a tap/ball valve.
I'm going to keep the loop clear to match the two tone black/chrome. While giving a bit of RGB sparkle from the distro plate, memory and graphics block.
I keep reading about stories of people using something in their loop to lubricate the pump. Then I read others to stay away from silver coil as it says that will void EK's warranty and cause flaking.