Trace

A programmatic approach using Trace:

Trace[
  BulletGauge[{1, 1.8, 3, 3.4, 4, 5}, {2.4, 2.9}, {0, 3.5, 4.8}],
  _ColorData
] // Flatten // First

ColorData[63, 1]

Check:

ColorData[63, "ColorList"]

Related examples:

• The default ColorFunction of DensityPlot before v10?

• Extracting unknown ColorFunction from Plot, Plot3D etc

Spelunking

This can also be found by spelunking the definition of BulletGauge itself using tools from:

• What is the most convenient way to read definitions of in-memory symbols when we don't have the source files? (Spelunking tools)

One find that the inner definition is Charting`iLinearGauge

Needs["GeneralUtilities`"]

PrintDefinitions @ Charting`iLinearGauge

Within that one finds a hard-coded color source:

Charting`padList[{{ColorData[63][#1] &, None}}, numvals]

Trace

A programmatic approach using Trace:

Trace[
  BulletGauge[{1, 1.8, 3, 3.4, 4, 5}, {2.4, 2.9}, {0, 3.5, 4.8}],
  _ColorData
] // Flatten // First

ColorData[63, 1]

Check:

ColorData[63, "ColorList"]

Related examples:

• The default ColorFunction of DensityPlot before v10?

• Extracting unknown ColorFunction from Plot, Plot3D etc

Spelunking

This can also be found by spelunking the definition of BulletGauge itself using tools from:

• What is the most convenient way to read definitions of in-memory symbols when we don't have the source files? (Spelunking tools)

One find that the inner definition is Charting`iLinearGauge

Needs["GeneralUtilities`"]

PrintDefinitions @ Charting`iLinearGauge

Within that one finds a hard-coded color source:

Charting`padList[{{ColorData[63][#1] &, None}}, numvals]

A programmatic approach using Trace:

Trace[
  BulletGauge[{1, 1.8, 3, 3.4, 4, 5}, {2.4, 2.9}, {0, 3.5, 4.8}],
  _ColorData
] // Flatten // First

ColorData[63, 1]

Check:

ColorData[63, "ColorList"]

Related examples:

• The default ColorFunction of DensityPlot before v10?

• Extracting unknown ColorFunction from Plot, Plot3D etc

Trace

A programmatic approach using Trace:

Trace[
  BulletGauge[{1, 1.8, 3, 3.4, 4, 5}, {2.4, 2.9}, {0, 3.5, 4.8}],
  _ColorData
] // Flatten // First

ColorData[63, 1]

Check:

ColorData[63, "ColorList"]

Related examples:

• The default ColorFunction of DensityPlot before v10?

• Extracting unknown ColorFunction from Plot, Plot3D etc

Spelunking

This can also be found by spelunking the definition of BulletGauge itself using tools from:

• What is the most convenient way to read definitions of in-memory symbols when we don't have the source files? (Spelunking tools)

One find that the inner definition is Charting`iLinearGauge

Needs["GeneralUtilities`"]

PrintDefinitions @ Charting`iLinearGauge

Within that one finds a hard-coded color source:

Charting`padList[{{ColorData[63][#1] &, None}}, numvals]