Depending on your chosen effect different parameters can be set.
One parameter that all of the FX have in common is the “Mix” parameter.
It defines how much the effect is mixed to the image / video file.
As long as it is set to the value 0 the effect is not visible.
Setting it to 100% (value 255) completely applies the effect.
See here two FX as example for different parameters:
Most of the FX consist of parameters that can be set by fader controls (see the Black Key in the image above). Some FX allow setting RGB values by an colour picker (see the Color Only effect in the image above).
The Color Picker is based on the RGB (Red, Green, Blue) color model, including faders for HSB (Hue, Saturation, Brightness).
You might set the desired color by entering the values for red, green and blue manually above the color field. Note that the bar between the field and the values show the corresponding values for HSB and is colored in the chosen color instantly. If you want to see the color in the color field (marked with a black outlined circle, click the white arrow.
Another way is clicking on the desired parameter at the bottom of the color picker (R,G,B,H,S or B) and using the little horizontal fader right above the parameter or picking a color directly from the color field.