Settings

One file: lanestyle's `data/lanestyle.json`, with a `lanestyle.json` in the current folder on top.

Your lanestyle.json states only what it changes, as roadstyle's settings do:

{"lanes": {"colors": {"bus": "#e8590c"}, "lines": {"dash_m": 2.0}}}

key	default	what
colors.auto / bus / bike / walk	#a3a3a3 / #d6336c / #1c7ed6 / #f0cb8c	a lane by its use (car lanes are drawn invisible; the road is in auto)
colors.groups	walking #f0cb8c, cycling and walking+cycling #1c7ed6	a road cars do not use, by who uses it
default_width_m	3.25	a lane with no width tag
width_m_by_use	walk 2.0, bike 1.5	an untagged footpath, an on-road bike lane
path_width_m	footway 2.0, steps 2.0, path 1.5, pedestrian 5.0, service 3.0, residential 3.0, track 2.5, default 2.0	a road without lanes (footway, steps, path, a walking-only service road ...) with no OSM width tag, by its class
casing_m / casing_min_px	0.14 / 1	the road's outline, metres, and at least this many pixels
centre_line_m	0.15	the gap between two directions, where the centre line lies
lines	dashes 3 m / gaps 9 m, 0.15 m wide, #f2f2f2, from zoom 17	lane lines (divider, centre switch them)
junction_trim_m	1	a lane line stops this far before its lane's end
arrows	end_m 10, repeat_m 0, at_junctions true, from zoom 18	turn arrows: before the lane's end, again every repeat_m (0: once)
zebra	stripe_m 0.5, gap_m 0.5, from zoom 17	painted crossings
sidewalk	width_m 2.0, from zoom 17	sidewalks a street's tags name
tunnel_body	#f6f4ee	the ground colour a tunnel's paint is faded toward

The road's own look (tunnels, bridges, names) is roadstyle's: a roadstyle.json in the current folder (roadstyle's settings).