Off the top of my head... (ok from Gemini)

The reason more males than females are color blind is primarily due to genetics, specifically how the genes for color vision are inherited on the X chromosome. This is known as X-linked recessive inheritance.

Here's a breakdown:

Chromosomes and Sex Determination:

Females typically have two X chromosomes (XX).

Males typically have one X and one Y chromosome (XY).

The genes responsible for the most common types of color blindness (red-green color blindness) are located on the X chromosome.

Recessive Trait: Color blindness is caused by a recessive gene. This means that a person needs to inherit two copies of the faulty gene (one from each parent) for the trait to be expressed, unless they only have one X chromosome.

Why Males are More Affected:

Males have only one X chromosome. If that single X chromosome carries the faulty gene for color vision, they will be color blind because there's no second X chromosome to provide a healthy, dominant gene to compensate.

Females have two X chromosomes. If a female inherits one X chromosome with the faulty gene, her other X chromosome usually carries a normal, dominant gene that can compensate, allowing her to have normal color vision. In this case, she is a "carrier" and can pass the gene on to her children, but she is not color blind herself. For a female to be color blind, she would need to inherit a faulty gene on both of her X chromosomes, which is much less likely.


In summary:

Males: 1 in 12 are affected by red-green color blindness.

Females: Only about 1 in 200 are affected by red-green color blindness.

This significant difference highlights the impact of X-linked inheritance on the prevalence of color blindness between the sexes.

 

Yes ... we're aware that our balance in this and other aspects differs from both the general population and from rail users.

 
Am I correct in thinking that this forum is predominantly male?

regarding the colour blindness condition.

Only one in 200 females suffer from the condition 

Not sure why nature has decided that one in 12 males should suffer from the condition,

thankfully I am not one of them.

 
I would agree that the colours that ontimetrains use - in my example - concern me because of how visible of otherwise they might be to people who are colour blind.  As happens sometimes, what starts as a light hearted question turns out to have some very serious corollaries.

 
Guidance for map design but useful for many application https://colorbrewer2.org/#type=sequential&scheme=BuGn&n=3

 

Yes, and remembering that red/green colour blindness is by far the most common form. In all but the most severe cases, a clear bright red and green can be distinguished, but dark red and dark olive green not so.

O/T trivia, but in the last war, the RAF actively recruited colour blind observers for some flights. Some types of yellow or green camo nets used by enemy forces, stood out from the surroundings but only to colour blind observers.

 
Colour blindness should also be a factor in compiling these coloured time tables.

 
I suppose I should not answer my own question - here are some examples, though, of how ontimetrains colours performance after the event.

 
BBQ charcoal for summer Sunday services.

 
From the Bala Lake Railway ...


What colours should be assigned to GWR timetabled for various days?