Coolant sitting low (3 door 2007 Yaris)

[douchenozzle]

While filling the windshield wiper fluid reservoir, i noticed that the pink engine coolant was sitting pretty low, just above the low level line on the indicator. 89,000 miles on it currently. Should I add a bit more coolant to fill it up to the full line and if so, what's the one to get? What does Toyota use originally? Does the cold effect coolant levels? Thanks for any help.