Mastering Geospatial Development with QGIS 3.x

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Knowing color picker components

Refer to the color picker tool screen to understand this section. The current and previous colors are displayed in the bottom-left corner of the color picker tool. In the Select Color window, the Old field depicts the color that is currently chosen, and the color mentioned in the Current field will replace the one in the Old field if the OK button is clicked. The current color can be saved in a quick-access color collection (the 16 colored squares in the bottom-right corner) using either of the following options:

By clicking on the button with the blue arrow (): This will save the current color in the first column of the top row of the color collection, overwriting any existing color. Subsequent clicks on the blue arrow button will store the current color in the next column until all 16 boxes are full and will then loop back to the beginning.
By dragging and dropping the current color on top of a quick-access color box: The old color can also be saved using the drag-and-drop method.

The color picker displays and allows for the manipulation of the value in the Current field in two color models: HSV and RGB. In the right half of the color picker, the hue (H), saturation (S), value (V), red (R), green (G), and blue (B) values for the currently selected color are displayed. Each of these color parameters can be individually modified by either using the slider controls or changing the numeric values.

Red, green, and blue values must be specified between 0 and 255, where 0 represents no color and 255 represents full color. Hue is specified in degrees ranging from 0 to 359, where each degree represents a different location (and color) on the color wheel. Saturation and value are specified using percentages and range between 0%, representing no saturation or value, and 100%, representing full saturation or value.

Below the color parameters is the Opacity setting. The right halves of the Current and Old fields display the color with the applied opacity level. For example, in the following screenshot, the current color is shown with no opacity (100%) on the left and with the currently selected opacity of 50% on the right:

The HTML notation textbox displays the HTML color notation of the current color. The color notation can be changed to one of the four different formats by clicking on the down arrow () in the HTML notation textbox.

Lastly, the Reset button resets the current color to match the old color.