My experience in regards to "brown or orange" curries is this: concentrated tomato paste (as is called for in most recipes) leaves a dark brown color in the curries. The stuff I get here is very strong concentrate and provides an after-taste that I personally dislike, so I often am using Passata (sieved tomatoes) instead, and these do not have such an impact on the color. So indeed, together with a "light yellowish" base (I use CBM), the curry comes out more with an orange color tone - but still it's more like a light brown rather than orange provided by food coloring. I use orange food color (and red) for my Tikka, so maybe that can have an impact on the color of the dish too.