Answered on September 17,2019
Ordinary Passport (Dark Blue) is issued to ordinary citizens for ordinary travel, such as for vacation, study and business trips (36 or 60 pages). It is a "Type P" passport, where P stands for Personal.
Official Passport (White cover) is issued to individuals representing the Indian government on official business. It is a "Type S" passport, S stands for Service.
Diplomatic Passport (Maroon cover) is issued to Indian diplomats, top ranking government officials and diplomatic couriers. It is a "Type D" passport with D stands for Diplomatic.
Tatkaal and SVP Passport: Tatkaal Passports (for urgent needs),and Short Validity Passport (SVP) are also available and these are generally considered Ordinary Passports once issued.
In addition, selected passport offices in India as well as overseas missions were authorised to issue regular Indo-Bangladesh passports and Indo-Sri Lankan passports to Indian nationals resident in West Bengal, the North-Eastern States, Tamil Nadu and Puducherry. These two passports respectively permitted travel to Bangladesh and Sri Lanka only and were not valid for travel to other foreign countries. India stopped issuing the Indo-Bangladeshi passport in 2013.