configuration file location
The configuration file is read from $XDG_CONFIG_HOME/a4/a4.ini by default. If $XDG_CONFIG_HOME is not set, it reads from $HOME/.config/a4/a4.ini. If $HOME is not set, it reads from ./a4.ini. Alternatively, the user can specify the configuration file path using the -c command line parameter. 
$ a4 -c ./a4_test.ini
specifying colors and attributes
In order to specify the appearance of an element, you give the foreground color, followed by the background color, followed by the font attributes. Specifying any of these is optional, but if you do specify any of them they must be in this order. You may choose the default color of the underlying terminal by specifying -1. 
titlebar_readonly = 1 -1 italic
titlebar_urgent   = 0xffffff 0xaaaaaa reverse,bold,single
Colors may be either an indexed color number, 0-255, or a specific 24-bit RGB color (see 8-bit, 256-color table). Indexed colors are the 8 standard colors (0-7), 8 bright colors (8-15), 216 extended colors (16-231), and 24 grayscale colors (232-255). Note that the actual color displayed when specifying an indexed color number is determined by how the underlying terminal defines the color for each index number. 24-bit RGB colors must be defined as a six digit hexidecimal number 0xRRGGBB where each of RGB is a hexidecimal digit 0-9, A-F, a-f. You may also specify a color as -1 to use the underlying terminal's default color.

Font attributes may be one of the following, although their implementation depends on the underlying terminal on which you are running a4. In order to combine any of attributes, separate them bya comman with no space.

bold italic reverse strike blink

You may also use one of these three underline types.

single double curly

default

titlebar elements

titlebar_selected
The currently selected or focused terminal window. If there is a group of focused windows they will all use these attributes.

layouts

actions

Actions are functions in a4 that may be assigned to keyboard sequences. There are a few "special" action keywords as well.

special keyword actions

startup
Any of the below actions that are assigned to the special keyword "startup" are run when a4 is initially started, in the order they are defined in the configuration file. Example

keyboard actions list

create_term
Create a new terminal. Default keybinding to C-g+c
zoom
Move the selected terminal to the top of the zoomed area. Default keybinding to C-g+Enter
toggleminimize
focusn
focusnext, focusnextnm, focusprev, focusprevnm
focuslast
togglegroupfocus
tag, toggletag
view, viewprevtag
hidestatusbar, showstatusbar, togglestatusbar
topstatusbarpos, botstatusbarpos, togglestatusbarpos
scrollbackpct, scrollbacklines
zoomnum, zoomsize
setlayout
quit_a4

mouse actions list

mouse_zoom
mouse_focus
mouse_scrollback

keysequences

colorschemes

colorrules

https://waxandwane.org