Such signals are called 'Distant signals'. You can identify them easily as they have a board with the letter 'P' written on it. These signals are somewhat like warning signals, indicating the state of the next main signal ( indicating whether the next signal is on green or red). Trains can always pass these signals no matter what they are showing. The combination of green and red in your photograph is a 'Caution' signal indicating that the next signal might be a red, or that there might be speed restriction up ahead.
These signals are usually placed at enough distance before the main signal so that trains can stop before reaching the main signal if necessary.
...
more...

Usually, the top lamp in these cases is a 2 color lamp; but in some cases, like the ghat sections where trains are always advised to go slowly, the red lamp on the top can be omitted, and the signal always put in 'Caution' mode as seen in your pic. And on ghat sections, since there are many speed restrictions, there will be many such signals between stations.