I don't try to keep their water cool or cold though that might help them cool off a little in the heat of summer. They don't sweat but cool themselves by breathing out warm moist air. Warm water does not concern me. I do try to keep it from getting hot. Hot could be a problem.
Dark absorbs heat, light reflects it. So anything exposed to the sun should be light in color or insulated. The chickens will peck and eat some types of insulation so be careful what you use or how you cover it up. In winter I use black bowls set in the sun for water. That helps keep it thawed when it drops below freezing. In summer I use white water bowls in the shade or in the coop to keep the water a little cooler.
Don't underestimate the value of shade. Shade can keep the rain barrel, your water lines, and the coop much cooler. You are in the northern hemisphere so your hottest directions with the sun are from the south or west. You might hang something on your run fencing to provide shade.
