My wife recently told me of my last batch of carefully, and only so slightly coloured Pilau Rice, that she would prefer it without the colour in future. The same applying to all of the other dishes I am to make is her preference. I am allowed to use Tumeric and Saffron or Safflower. I will oblige her with that wish for all the reasons Secret Santa points out and the concerns regarding "food additives" and both short and long term health implications.
On the other hand, this site is dedicated to BIR. There can be no argument that presentation is paramount to success in any kitchen. Colour, whether we like it or not, is a critical element of presentation.
So, for consumption by the family at home, it will be "au naturel" from now on with fresh foods as salad and vegetables for the colour. Fortunately for me, I usually make a variety of dishes that provide variation in colour anyway without artificials, but I guess the jar of Tandoori Colour powder I have is no longer required. Un-coloured Chicken Tikka from now on. Is this BIR (or Australian IR) practice? No. They use colour.
The Glascow curries are simply showing how it is being done in a working business, and this is completely relevant to this forum. The recipes can easily be made omitting the oils and colours or varied in other ways, as to better suite any individuals personal preference. This is what I intend to do and I appreciate these efforts made to share the experience in contemporary practices.