The Color Pencil 
is designed to draw free-form lines with hard edges.
You can change the pencil’s color using the Color panel, Swatches panel, Color Wheel panel, or by clicking the image with the Eyedropper tool. To pick a color sample, press and hold the I key and then click the image with the Eyedropper tool. After the hotkey is released, the painting tool becomes active again.
The basic tool settings are shown in the Tool Options panel above the Image Window or by right-clicking on the image. To display the full list of parameters, press the tool icon in the Tool Options panel or use the F5 key. To specify the parameter settings, enter a numerical value in the parameter’s field or use the slider.
Element - in the drop-down list, select the type of the basic element of the brush: Ellipse or Select Shape.
Size (1-5000). The maximum width of a line made by the brush (in pixels).
Opacity (1-100). The opacity of the pencil strokes against the color of the background. This parameter sets the opacity color, by which a line is drawn: at lower values, the color of the line is paler and its interaction with the color of the background increases.
Opacity = 25
Opacity = 75
Fill (1-100). The parameter determines the density of paint in the brush stroke. If you hold the mouse button while drawing, the strokes are overlapped and the filling effect increases (unlike the Opacity parameter). The smaller the parameter, the thinner and more transparent the layer of the color is. At the value = 100%, the brush strokes are as opaque as possible.
Fill = 25
Fill = 75
Blend Mode. It defines how the pencil strokes blend with the background. The program provides 27 blend modes.
Multiply Mode
Overlay Mode
In addition to the above-mentioned parameters, you can adjust the advanced settings that affect the shape and position of the brush marks.
Press the Default button to set all settings to their default values.
In order to draw a straight line, click the left mouse button at its starting point, then, press Shift, click the end point, and let go of Shift. If Shift is not released, a new line will be drawn to each point where the mouse is clicked.