Of "Tiger faces", "Barbie Dolls", "Baldies" and "Jumbos"

These are not some fictional characters in some movie, but "nick names" given to certain class of Indian Railway locomotive because of their appearance or color. Certain loco sheds prefer to paint their locos in specific color combinations (maybe also based on a specific class of locomotives).

A "Tiger face" can be seen adjacent. This one is a WAG-7 from Ajni shed. Its face has some stripes and so is called a "Tiger Face".
A "Jumbo" is here. This unusually sized WDM-2 from Guntakal shed is called so because of its larger than usual structure. Most of the "Jumbos" may have undergone structural changes because of accidents or damage.
A "Baldie" looks like this WDM-3A from Gooty shed. The hood of a "Baldie" sets it out from the other normal WDMs and hence the name. Again, this modification would have been necessary because of some accident or damage.
And, a "Barbie Doll" is named so because of its "lipstick" color combination. This one is a Tatanagar WAM-4.