How to let the chart user choose a colour

Call input.color once, at the top level, and pass what it gives you to the drawing.

input.color(const color defval, const string title, const string tooltip, const string inline, const string group, const bool confirm) → input color

indicator("Reader's colour", "usercol", true)

line_colour = input.color(color.blue, "Line colour")

plot(close, title = "Close", color = line_colour)

The first argument is the colour the control starts at. The second is its label.

If you want one colour for rising and another for falling

Declare two controls and choose between them in the colour argument.

indicator("Direction colours", "dircol", true)

up = input.color(color.green, "Rising", group = "Appearance")
down = input.color(color.red, "Falling", group = "Appearance")

plot(close, title = "Close", color = close > close[1] ? up : down)

What you get back

An input color, not a const color. The input form sits above const in the ordering of forms, so the reader’s choice is accepted where a simple or series colour is wanted, and refused where a const is required.

The failures to watch for

• An input argument cannot be na. The interpreter rejects it. Give the control a real default colour.
• The default is a const color, so a named constant or a hex literal will do and a value read off a bar will not.

See Inputs and Colour and transparency.