From the 1930s onward, as celluloid and casein became popular, colourful pens were available at the same price as black ones. And yet it was the black pens that many people bought. Right through until fountain pens were replaced by ballpoints more black pens were bought than any other colour.
Why? I don’t suppose we will ever really know but for much of the first half of the twentieth century, men avoided colour in dress and many other things. Black suit, black bowler hat, black shoes, white shirt and a conservative tie. In that atmosphere it is perhaps natural that many chose a black pen.
Wishing to give the impression of seriousness helped the choice of the black pen. Bright, colourful celluloid patterns might give all the wrong impressions. Though it is much less prevalent now that attitude has not gone away entirely. I see many black Montblancs and many of the more expensive Japanese pens come in black.
The average pen buyer today prefers colour, unless the nib of the vintage black pen is exceptional in some way: flexible, a stub or an oblique. The black pens with firm medium nibs take longer to move. For that reason, when shopping for stock I buy colour whenever I can but there are weeks when eBay offers nothing but black Swans and Blackbirds.
For myself I am perfectly happy with black vintage pens. I only care about how they write. I love late thirties/wartime Swan Leverless 1060s and 0160s. I have two of each and they are the pens I most enjoy using. Green or blue marbled pens of the same type would be equally welcome if they wrote equally well but I don’t buy for colour for myself.
A long time ago, when pen collecting took off, many collectors only bought black pens as they believed them to be the best example of the model, without the distraction of colourful patterns. That held true for a time until people began to appreciate the beauty of the various patterned pens. Now some vintage pen collectors want an example of each model in all the colours then offered. Some colours are less common and fetch higher prices.
I’m writing this with a metal Pilot with a pattern of roses on the cap and barrel. If it was black with the same gorgeous nib I would be equally happy with it but I do enjoy the pattern and colours that someone decided upon many years ago.