Please note the next sentence is not intended to be rude, I'm quite serious. Do you suffer from any particular colour blindness issue?

If you are not seeing the colours correctly and you do not suffer from a colour blindness issue then your computer or graphics driver settings may not be set up correctly.

The image you posted has a full range of colours. Red, pink, crimson, lilac,purple, aquamarine, mid, light and dark blues, vivid bright green, yellow-green, blue-greens, dark greens, khaki, light and mid yellows, oranges, mid and dark browns, greys, black, white and they are just the 'Basic colours'.

The first colour on second line on far left as selected by you in image, is red. Red has the RGB(Red,Green,Blue) colour setting: rgb(255, 0, 0) - this is indicated on the far bottom right in image. 255 is the maximum setting, so it is as red as you can get as it does not have any green or blue colour in that colouration.

The black arrow pointer you see middle of far right side points to a slider which means you can change the values to lighten or darken the starting colour choice eg: deepen colour by reducing red count and decreasing luminosity (lightness as some people call it).

You can also click the mouse in the rainbow zone and depending upon where you click, that colour will appear in the lower 'Colour/Solid' box with it's corresponding Values on the right side.

The following link is an excellent way of explaining what Hue, Saturation and Luminosity/Lightness setting can do to effect a colour. https://www.w3schools.com/colors/colors_picker.asp

I think you may have a setting that is wrong for your graphics card or computer is using a default windows card which is not exactly very good. Is your graphics driver up to date ? Find out what graphic card you use eg: Nvidia Is the computer actually using that graphics card or is it failing? check out what colour setting you should have as setup. Is computer perhaps getting too hot? This is not the forum to offer help with those types of issues, but it does sound like you have a problem with the graphics card.

I've never had a problem with color blindness before so I think your idea about the graphics card is most helpful. I use two different computers - a PC which is almost 8 years old and a relatively new Macbook Air. It's the PC on which I am having the problem. When I look at the colors on the Mac, everything is fine. So, thanks for pointing me in the direction of the real problem!