Section 17(2) in The Bangalore Metro Railway (General) Rules, 2011
(2)Fixed Signals -(i)On main lines, fixed signals are color light signals capable of showing a "Red", "Violet' or "Green" aspect;(ii)a "Red" aspect indicates that a train must be brought to Stop short of the signal;(iii)a "Violet" aspect indicates that the route is set and locked but may not be fully clear and a train operating under cab signals may proceed under the authority of the cab signals but a train operating on the sole authority of line side signals must stop and seek instructions from the Traffic Controller;(iv)a "Green" aspect indicates that the route is cleared to the next fixed signal and the train may proceed as far as the next fixed signal;(v)when a fixed signal is not in use, the aspect shall be covered and the cover shall display two crossed white bars on a black background, the bars being not less than 30cm long and 10 cm wide.
