The subpixel order specifies the order of color elements within each pixel on the display device when rendering with an antialiasing mode of :subpixel.

(defcenum cairo-subpixel-order-t
  :default
  :rgb
  :bgr
  :vrgb
  :vbgr)  

:default

Use the default subpixel order for the target device.

:rgb

Subpixel elements are arranged horizontally with red at the left.

:bgr

Subpixel elements are arranged horizontally with blue at the left.

:vrgb

Subpixel elements are arranged vertically with red at the top.

:vbgr

Subpixel elements are arranged vertically with blue at the top.