These images are created from the EUVI band of the STEREO Ahead & Behind
Telescopes.
The STEREO images were set as follows:
EUVI-171 - Blue
EUVI-195 - Green
EUVI-284 - Red

Offsets are applied to keep the images at a constant background range.
This is done for each band of EUVI.
They are then put through Trichomy (RGB) in AstroArt 3.0 and reduced to 80%
Gamma is lowered to compensate for changing light levels so as to make the images consistently show as much structure as possible.

These images are intended to be instructive and correlate with visible Solar Activity as seen from Earth.
They are known as Composite EIT's after the SOHO Ultraviolet series, or 
CEIT for short.
Some viewers may note the resemblance to contemporary narrowband images.

For Dr. Leif Svalgaard:

Robert Bateman
Musser Hill Observatory
Weaverville, CA