Reasoning back in the day for coloured backgrounds

[retro space]

What puzzles me like crazy, is that many home computers of the eighties, the CPC off course, but also the C64, ZX Spectrum, MSX to name a few had a coloured background.

Why weren't they just black? With a 50Hz PAL TV it makes no sense to have such a large flickering rectangle in front of you. It also increases wear of the phoshor, energy use, colour fringes and it lowers readability. No to mention that the coloured borders emphasize the bubble-shape of the tube, where a black border gives a more rectangular feel of the image. Last problem is overscan areas.... We all remember the NES having those dirty sides when scrolling.

If I turn on my P2000T it feels so nice to have just white text on black.
Does anybody have a link to a story about the why of coloured backgrounds? I can't find any positive aspect to it. One assumption could be marketing.... That you could see in a single shot of the TV what system was connected.

[eto]

Probably to make clear to the potential buyer that this system can display colours. Imagine the CPC sitting next to a C64 on the shelf of a store - but the CPC has a black/white display instead of bright yellow/blue.

[Brocky]

also the colours chosen for the CPC where the be the best combination for contrast on green screen while still keeping colour
 
it could be the case that other computers like the C64 used that combo for b&w TVs are they where still common at the time

[retro space]

Probably to make clear to the potential buyer that this system can display colours. Imagine the CPC sitting next to a C64 on the shelf of a store - but the CPC has a black/white display instead of bright yellow/blue.

That makes no sense. The ZX Spectrum 128 for example had a white background, but had a nice coloured boot logo. The P2000T, the worst machine when it comes to colour and graphics, just shows the BASIC version text in 3 different colours. The MSX had that nice scrolling logo, but it would have been even more impressive when the logo had multiple colours. To show colour capabilities, using the background colour for it is the worst idea IMO.

[retro space]

also the colours chosen for the CPC where the be the best combination for contrast on green screen while still keeping colour
 
it could be the case that other computers like the C64 used that combo for b&w TVs are they where still common at the time

I don't know why it would make sense to use a limited range of contrast for a monochrome display. Those always have brightness & contrast control. If you send white on black text, you could every bit as much turn it to a dark grey background with light grey text. But not always the other way around. Try to turn away the "green" on the CPC monitor, even if you set the background to black. Even the GUI B&W machines, like Apple Plus and Atari ST, had black borders around the interface that was dominantly white.

[Brocky]

on the cpcs its something to do with using LUMA pin on the green screen..

iirc borders was coz of hardware/memory limitation and so text wasnt displayed off the edge of the CRT screen..every individual CRT displays the picture different so they built in margins to compensate and make sure the text can always be seen..
eg. some TV would display the main CPC and C64 image with the corners right in the CRT corner... and the border be mostly hidden by the "bezel" that hides the front edge of the tube..

[andycadley]

Probably because someone thought it "looked good".

You have to keep in mind that everything was very new then. Nobody really knew what was best. I suspect putting some colour on the screen helped to sell the concept that the computer could display colours, but the how and why would just be whatever someone thought of and could implement easily.

[McArti0]

Elan Enterprice 64/128 is black with color fonts.

[Anthony Flack]

Back in the days when home computers had RF output, having a coloured bootup screen did make it easier to tune in the picture in.

Remember tuning the picture in? Remember when TVs actually had physical dials for tuning the channels with, and you maybe only had four presets on the TV? And auntie doesn't want you to use the computer on her TV and if you do, you had better tune the channel back in afterwards.

[McArti0]

maybe only had four presets

maybe three ...

[dodogildo]

Back in the days when home computers had RF output, having a coloured bootup screen did make it easier to tune in the picture in.

Makes much sense.

[chinnyhill10]

The reason the CPC has a blue background with yellow text at the startup was because Orion told Amstrad that this would give the best quality colour display on startup for the CRT's they were supplying. That's it.

Green screen doesn't come into it otherwise you'd have ink 0 for the background and ink 26 for the text. But if you did this you wouldn't get the 'mugs eyeful' of a colour display in Dixons. It all revolved around selling colour units.

[dodogildo]

I wonder how many more color monitors were sold than green monitors?
(Mine was green.)

[Prodatron]

I wonder how many more color monitors were sold than green monitors?
(Mine was green.)

Good question.
When checking eBay it seems that there were >= 10x more green monitors than colour ones.