What was Doraemon's original factory color?

Okay, let me explain this for you!

Doraemon's original factory color was yellow!

That's right! You might be used to the familiar blue "Blue Cat" we all know, but when he first came out of the robot manufacturing plant, he was actually yellow and had pointy ears.

So why did he become the way he is now? There's actually a rather "tragic" story behind it.

The Transformation from Yellow to Blue

This story is detailed in the Doraemon special episode "The Birth of Doraemon (2112)". In short, here's what happened:

Ears Bitten Off by a Mouse: One day, while Doraemon was taking a nap, his ears were chewed off by a robotic mouse. This left him extremely sad and depressed.
Drank the Wrong Potion: To cheer himself up, he tried to drink some "Cheer-Up Potion". But in his panic, he grabbed the wrong bottle and drank "Tragedy Potion" instead. This made things worse, and he became even more sorrowful, starting to cry uncontrollably.
Cried Until His Paint Came Off: He cried non-stop for three days and three nights. His tears washed off the yellow paint finish (essentially the paint), revealing the blue base coat underneath.
His Voice Changed Too: Because he cried for so long, his voice became hoarse. So his originally higher-pitched voice changed into the raspy voice we're familiar with today.

Therefore, Doraemon is blue, earless, and has a hoarse voice all because of this "workplace accident" caused by the mouse bite.

A Fun Little Fact

Why is Doraemon so afraid of mice? Precisely because of this traumatic experience. Mice left him with a huge psychological scar, which is why he becomes terrified out of his wits whenever he sees one.
Why is his sister, Dorami, yellow? Dorami is a later model, superior-performance robot. She didn't experience her brother's tragic ordeal, so she retained her original factory yellow paint and ears (hers are bow-shaped). Looking at her, we can see what Doraemon originally looked like.

Hope this explanation clears things up! Next time you see Doraemon, you'll know that his blue exterior holds a sad story.