I guess that it boils down to a matter of perception....which is more important - taste or appearance . As CP previously pointed out , most base sauces will produce that well known greenish-brown hue . If you wish to disguise the colour , so be it....but maintain the taste ! Since most traditional / BIR recipes fall into this section of the colour spectrum , I really don't think that most curry aficionados will give one...perhaps two hoots about colour .