I need to create a choice list for user to use color for figure interactively. User also able to choose muliple values depending on the number of rasterlayer in use.
It appears you marked it answered before you got any, but non-the-less
depends on the tool type, but you might need a value list
Defining parameters in a Python toolbox—Help | ArcGIS for Desktop
but that depends on the type of toolbox
Comparing custom and Python toolboxes—Help | ArcGIS for Desktop