Calcium K Solar Image

Sorry, a belated praise from me, great images in Calcium K, Rupert.  That link you posted on what can be observed between white, HA and CaK was extremely informative.  Bookmarking for future reference.  I personally love the blue colour and as you say, it makes a statement, "I am Calcium K and blooming proud of it".  The blue colour actually seems to give the best contrast so far.

Any of you who have not seen Ruperts previous images before should take a look at the gallery where he shows a great comparison between the white light and Calcium K of the same portion of sun,  The Ca-K hs by far more features and overall better definition to boot.

http://flamsteed.info/image-gallery/nggallery/galleries/the-sun

But generally, I think its fine to use whatever colour looks pleasing for presentational purposes.  Orange is absolutely lovely in my view but it can be at the sacrifice of contrast.  However, dont forget  monochrome cameras capture the most details on the sensors  so tinting the image with an artificial colour is inevitable anyway.  Of course, they can present the image in monochrome which also looks really good.   But from an all out attractive presentation, orange really wins out for me and its only because our mindset visualises the sun in that colour (or yellow)...although that does seem to depend on culture as Mike points out children draws the sun red in Japan.