As per the Press Release: 2017-2018/481 by RBI
The Reserve Bank of India will shortly issue Rs 50 denomination banknotes in the Mahatma Gandhi (New) Series, bearing signature of Dr. Urjit R. Patel, Governor, Reserve Bank of India. The new denomination has motif of Hampi with Chariot on the reverse, depicting the country’s cultural heritage. The base colour of the note is Fluorescent Blue. The note has other designs, geometric patterns aligning with the overall colour scheme, both at the obverse and reverse.
All the banknotes in the denomination of Rs 50/- issued by the Reserve Bank in the earlier series will continue to be legal tender.
The image and salient features of Rs 50 denomination banknote in the Mahatma Gandhi (New) Series are as under:
Obverse (Front)
1. See through register with denominational numeral 50
2. Denominational numeral ५० in Devanagari
3. Portrait of Mahatma Gandhi at the centre
4. Micro letters ‘RBI’, ‘भारत’, ‘INDIA’ and ‘50’
5. Windowed demetalised security thread with inscriptions ‘भारत’ and RBI,
6. Guarantee Clause, Governor’s signature with Promise Clause and RBI emblem towards the right of Mahatma Gandhi portrait.
7. Ashoka Pillar emblem on the right.
8. Mahatma Gandhi portrait and electrotype (50) watermarks.
9. Number panel with numerals growing from small to big on the top left side and bottom right side.
Reverse (Back)
10. Year of printing of the note on the left.
11. Swachh Bharat logo with the slogan.
12. Language panel.
13. Motif of Hampi with Chariot.
14. Denominational numeral ५० in Devanagari.
The dimension of the banknote will be 66 mm x 135 mm.
Well going into the history of Rs 50 Indian currency note, the Rs 50 banknote denomination was first introduced by the Reserve Bank of India (RBI) in 1975 as a part of the Lion Capital Series, which had the Ashoka pillar on the banknote. 
Later it was replaced by a watermark of Mahatma Gandhi in the Mahatma Gandhi Series, in 1996 
