Around here the civilian rescue helicopters are painted in bright yellow.
Traditonally some missions are flown by army helicopters. Some search missions are flown by law enforcmement helicopters and in very rare cases by recon Tornadoes. Those aircraft are painted in the color schemes of their service. They are used for other missions too.
When they still had the Iroquois, it was kind of iconic and easily recognizeable by the red cross on a white background on the side.