Setting the font for all captions
To set the font for all the axis captions and the pagelabels:

ch.Set 'Cfont' 'ti,12,teal'

The short code for the font is a two-letter mnemonic followed by either or both of the letters ‘b’ and ‘i’ for the bold and italic variants. The font size is in points, and colours are the usual set of internet names or ‘#FF’ style values.

Setting x,y,z captions independently
You may over-ride this setting for any of the x,y,z captions independently with the XCaptionFont, YCaptionFont and ZCaptionFont properties. These properties may be used in conjunction, for example:

ch.Set ('Cfont' 'arb,14,Navy')('CYFont' 'Maroon')

Note that the ordering is important here – the generic font must be set first.

See also ...
Colour Cycle
Fonts – defining and using short codes