If our eyes could see colors in this part of the electromagnetic spectrum, surely they would see these colors.
In NGC 2237 ionized hydrogen and sulfur are the two components of this area mostly hot gas, so we would tend to see orange red.
In the center circle, but this element is oxygen, so we would see teal blue.
This huge cloud of gas and dust born NGC 2244, this open cluster that lies at the center of the nebula and thanks to its heat and ionization enables the brightness of this gas.
This image was taken with a CCD camera in Ha (14 hours) OIII (14 hours) and IBS (9 hours), 37 hours total exposure, from near the city of Valencia (Spain)
The capture was made by Alfonso Carreno (MPC J09) = http://http://www.zonalunar.com/
and processed by Ferran Bosch (space_colors) = http://www.caliu.fotografiaastronomica
100% size: http://caliu.fotografiaastronomica.com/Roseta_narrow_full.jpg
I hope you enjoy