One can set default style and inputs values for newly created indicators using studies_overrides parameter. Its value is expected to be an object where key is a path to property being changed and value is the new value for it. Example:

studies_overrides: {
    "volume.volume.color.0": "#00FFFF",
    "volume.volume.color.1": "#0000FF",
    "volume.volume.transparency": 70,
    "volume.volume ma.color": "#FF0000",
    "volume.volume ma.transparency": 30,
    "volume.volume ma.linewidth": 5,
    "volume.show ma": true,
    "bollinger bands.median.color": "#33FF88",
    "bollinger bands.upper.linewidth": 7
}

In the example above, in example, all created Bollinger Bands will have upper line width = 7 (unless you create it through API and have specified another value for this line).

How to set study name

You should use studies names as-they-are in the Insert Study dialog, but in lower case. So if you want to override default EMA's length, try using moving average exponential.length. The same principle works for inputs names: use names as you can see them in Study Properties dialog (use lower case also). Example: stochastic.smooth d.

Compare

You can customize new series added via Compare. Use compare.plot to customize the line and compare.source to change the price source:

"compare.plot.color": "#000000",
"compare.source": "high"

Overlay

Since 1.12 to customize Overlay you may use the following properties:

Overlay.style: (bars = 0, candles = 1, line = 2, area = 3, heiken ashi = 8, hollow candles = 9)
Overlay.showPriceLine: boolean

Overlay.candleStyle.upColor: color
Overlay.candleStyle.downColor: color
Overlay.candleStyle.drawWick: boolean
Overlay.candleStyle.drawBorder: boolean
Overlay.candleStyle.borderColor: color
Overlay.candleStyle.borderUpColor: color
Overlay.candleStyle.borderDownColor: color
Overlay.candleStyle.wickColor: color
Overlay.candleStyle.barColorsOnPrevClose: boolean

Overlay.hollowCandleStyle.upColor: color
Overlay.hollowCandleStyle.downColor: color
Overlay.hollowCandleStyle.drawWick: boolean
Overlay.hollowCandleStyle.drawBorder: boolean
Overlay.hollowCandleStyle.borderColor: color
Overlay.hollowCandleStyle.borderUpColor: color
Overlay.hollowCandleStyle.borderDownColor: color
Overlay.hollowCandleStyle.wickColor: color
Overlay.hollowCandleStyle.barColorsOnPrevClose: boolean

Overlay.barStyle.upColor: color
Overlay.barStyle.downColor: color
Overlay.barStyle.barColorsOnPrevClose: boolean
Overlay.barStyle.dontDrawOpen: boolean

Overlay.lineStyle.color: color
Overlay.lineStyle.linewidth: integer
Overlay.lineStyle.priceSource: open/high/low/close
Overlay.lineStyle.styleType: (bars = 0, candles = 1, line = 2, area = 3, heiken ashi = 8, hollow candles = 9)

Overlay.areaStyle.color1: color
Overlay.areaStyle.color2: color
Overlay.areaStyle.linecolor: color
Overlay.areaStyle.linestyle: (solid = 0; dotted = 1; dashed = 2; large dashed = 3)
Overlay.areaStyle.linewidth: integer
Overlay.areaStyle.priceSource: open/high/low/close

Syntax

Property path is a set of lower-case identifiers splitted with dot (.). Path formats are described below.

Remark: If a plot/band/area/input name is the same you can get an error. In this case you can specify an exact destination that you want to change by adding :plot, :band, :area or :input to the path. (e.g. short:plot.color)

Study input

Format: indicator_name.input_name

indicator_name: use name as you can see it in Indicators dialog.
input_name: use name as you can see it in indicator's properties dialog (for example, show ma)

Examples: volume.show ma, bollinger bands.length

Plot property

Format: indicator_name.plot_name.property_name

indicator_name: < ... >
plot_name: as you can see it in indicator's properties dialog (for example, Volume or Plot)
property_name: one of the following:
- transparency
- linewidth
- plottype. Supported plot types are:
  - line
  - histogram
  - cross
  - area
  - columns
  - circles
  - line_with_breaks
  - area_with_breaks

Examples: volume.volume.transparency, bollinger bands.median.linewidth

Plot colors

Format: indicator_name.plot_name.color<.color_index>

indicator_name: < ... >
plot_name: < ... >
color. It is just a keyword.
color_index (optional): color index (if any). It's just an ordinal number of a color for this plot. I.e., to replace the color which is green by default for Volume, one should use color_index = 1.

Remark 1: color.0 is a synonym of color .So paths volume.volume.color.0 and volume.volume.color are treated to be the same.

Remark 2: For now, customizing area fill color and transparency is not supported.

Limitations:

Only #RRGGBB format is supported for colors. Do not use short format #RGB.
Transparency varies in [0..100] range. 100 means plot is fully opaque.
Thickness is an integer.

Default precision

Since 1.6 you can change default precision of studies using name.precision format. Example:
"average true range.precision": 8

Studies-Overrides