Tandoori masala is a mixture of spices specifically for use with a tandoor, or clay oven, in traditional north Indian and Pakistani cooking. The bright red colour you sometimes see is a food colouring, and unnecessary. Paprika and cayenne can contribute to the redness.
 
Mix with a little oil, and rub under the skin of a chicken before roasting, sprinkle over cauliflower before sautering, or mix with yoghurt as a marinade before barbecuing or grilling.