The history object as a whole provides a simple way to navigate through drilldown charts. Modifying the item: {} object inside of history: {} allows you to style the arrows associated to the navigation.

Attribute	Type	Description
alpha	Number	Sets the opacity on the marker, with 0 being fully transparent and 1 being fully opaque. Note that decimal value requires the leading 0. Default Value: 1
angle	Number	Sets the rotation angle of the object.
backgroundColor background-color	String	Sets the background color of the object. Colors can be entered by name (e.g., "purple", "blue"), hexadecimal notation (e.g., "#666699", #33ccff"), or RGB notation (e.g., "rgb(255,0,0)", "rgb(0,0,255)") Default Value: null
backgroundColor1 background-color-1	String	Sets the first color of a 2 color background gradient of the object. To be used with background-color-2. Default Value: null
backgroundColor2 background-color-2	String	Sets the second color of a 2 color background gradient of the object. To be used with background-color-1. Default Value: null
border	Number	Sets the border width of the object. Can be a single value or a string of values, setting the values in the order "top right bottom left"
borderAlpha border-alpha	Number	Sets the transparency level of the border on the object. Values must range between 0.0 and 1.0, with 0.0 being completely transparent and 1.0 being completely opaque. Note that values require the leading 0 before the decimal point. Default Value: 1 Introduced in: v2.1.1
borderColor border-color	String	Sets the border color of the object. Default Value: '#000'
borderWidth border-width	Number	Sets the border width of the object. Default Value: 0
class	String	Sets a class value on the object. Default Value: null
dataN data-n	Any	Prefix attribute or array using "data-" to define a custom token.
fillAngle fill-angle	Number	Sets the angle of the axis along which the linear gradient is drawn. Default Value: 90
fillOffsetX fill-offset-x	Number	Sets an X offset to apply to the fill. Default Value: 0
fillOffsetY fill-offset-y	Number	Sets a Y offset to apply to the fill. Default Value: 0
fillType fill-type	String	Sets the background gradient fill type to either linear or radial. Accepted Values: ['linear', 'none', 'radial'] Default Value: 'linear'
gradientColors gradient-colors	String	Sets a set of colors for a complex background gradient consisting of 2 or more colors. To be used with gradient-stops. Default Value: ''
gradientStops gradient-stops	String	Sets the gradient stops for a complex background gradient consisting of 2 or more colors. To be used with gradient-colors. Default Value: ''
height	Number	Sets the object's height.
id	String	Sets the id of the object. Default Value: ''
lineColor line-color	String	Sets the line color of the object, applicable on non-closed shapes. See also border-color for closed shapes. Default Value: '#000'
lineGapSize line-gap-size	Number	Can be used to create custom dashed or dotted lines when used with line-segment-size. This will control the size of the gaps between each line segment. Default Value: 0
lineSegmentSize line-segment-size	Number	Can be used to create custom dashed or dotted lines when used with line-gap-size. This will control the size of the visible segment of line. Default Value: 0
lineStyle line-style	String	Sets the line style of the object. Accepted Values: ['dashdot', 'dashed', 'dotted', 'solid'] Default Value: ''
offsetX offset-x	Number	Sets an x-offset to apply when positioning the object.
offsetY offset-y	Number	Sets an y-offset to apply when positioning the object.
shadow	Boolean	Sets whether the object's shadow is visible or not. Has limited effect on HTML5 implementation. Default Value: false
shadowAlpha shadow-alpha	Number	Sets the transparency of the shadow of the object. The higher the value, the less transparent the shadow will be. Default Value: 0.75
shadowAngle shadow-angle	Number	Sets the angle of the shadow underneath the object. Default Value: 45
shadowBlur shadow-blur	Number	Sets the blur effect size for the shadow of the object. Has limited effect on HTML5 implementation. Default Value: 0
shadowColor shadow-color	String	Sets the color of the shadow of the object. Default Value: '#999'
shadowDistance shadow-distance	Number	Sets the distance between the shadow and the object. Default Value: 2
visible	Boolean	Sets the visibility of the object. Allows you to turn off the object without removing lines of JSON. Default Value: true
width	Number	Sets the object's width.
x	Number	Sets the X position of the object. Default Value: -1
y	Number	Sets the Y position of the object.
zIndex z-index	Number	Sets the z position of the object. Objects with higher z indexes will appear "above" those with lower z index values. Default Value: 1