https://webprog3.com,sametab
Click on the palette to choose your colour. Its value will then be shown in RGB and hexadecimal.
If you do not find the colour you want, then go to the next palette by clicking on the rightmost palette arrow.
Again, either choose your colour by clicking on the palette, or advance to the next one by clicking on the rightmost palette button.
If you wish, you can return to the first palette instead by clicking on the left palette button.
The third and last palette allows you to choose your colour by name.
It's quite a long list, so use the scrollbar on the right.
If you click on the rightmost palette arrow again, it will simply show you the first palette, to save you clicking twice on the left palette arrow to get to it.
When you have chosen your colour, click on the OK button as shown, or on Cancel if you no longer wish to choose a colour. This will close the Chooser.