seabird

seabird is a theme based on hue 204 .

• available for Vim, terminals, and other stuff
• mathematically derived, incorporating two contrast ratio standards (ISO 3:1, W3C 'AA' 4½:1)
• comes in four variants

seabird variants	light theme	dark theme
high-saturation	seagull	petrel
low-saturation	grey gull	storm petrel

screenshots

SEAGULL		PETREL
GREY GULL		STORM PETREL

Vim theme

step 1: download the colour scheme

option A: manually

Download the desired colourscheme files and place in directory ~/.vim/colors/ (Linux/Mac) or %userprofile%\vimfiles\colors\ (Windows).

option B: using a plugin manager

For easy management of Vim colour schemes (and other plugins), try a plugin manager. With vim-plug, for instance, just add Plug 'nightsense/seabird' to the list of plugins in vimrc, then run PlugUpdate.

step 2: activate the colour scheme

To activate the seagull theme, add colorscheme seagull to the vimrc file. Choose from among seagull, greygull, petrel, and stormpetrel.

For Neovim, add set termguicolors to enable truecolour support.

To switch automatically between a 'day theme' and 'night theme', try the night-and-day plugin.

step 3: configure terminal colours (if using Vim in a terminal)

In order for seabird to work properly in terminal Vim, set the terminal's colours to match those of the active Vim theme.

terminal themes

As of now, this repository provides the following terminal configuration files:

• Xresources files for xterm and urxvt (Linux)
• .colorscheme files for Konsole and QTerminal (Linux)
• gsettings 'command blocks' for pantheon-terminal (elementary OS)
• .terminal files for terminal.app (OSX)
• .itermcolors files for iTerm2 (OSX)

For gnome-terminal, see this repository.

Configuration files for other terminals may be added if requested.

other themes

• VS Code
• Intellij

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how seabird took flight

step 1: choosing a principal hue

Hue 204 was chosen because:

• a sky blue colour was desired
• at 100% saturation and value, hue 204 features 3:1 contrast ratio (the ISO standard) with a white background

step 2: choosing base colours

The base colours, which are shared by the light and dark versions of seabird, were selected using the hue/saturation/value model of colour definition.

First, all base colours were assigned hue 204.

Second, saturation levels were assigned. The lightest colour, seagrey8, was assigned 0. For the remaining colours, an excerpt of the Fibonacci sequence was applied.

base colour	role	hue °	saturation %
seagrey1	regular background (petrel)	204	55
seagrey2	highlighted background (petrel)	204	34
seagrey3	subdued text (petrel)	204	21
seagrey4	regular text (seagull)	204	13
seagrey5	regular text (petrel)	204	8
seagrey6	subdued text (seagull)	204	5
seagrey7	highlighted background (seagull)	204	3
seagrey8	regular background (seagull)	204	0

Third, value levels were assigned. seagrey8 was set to 100% value. The rest were assigned values based on contrast ratios with other base colours.

this colour was assigned...	...this value...	...to meet this contrast ratio...	...with this colour
seagrey1	10	18½:1	seagrey8
seagrey2	17	1⅕:1	seagrey1
seagrey3	48	3:1	seagrey2
seagrey4	49	4½:1	seagrey8
seagrey5	51	4½:1	seagrey1
seagrey6	53	3:1	seagrey7
seagrey7	93	1⅕:1	seagrey8
seagrey8	100	-	-

• the 18½:1 ratio ensures a 10% value background for the dark theme: a "soft black" good for long-term readability
• the 1⅕:1 ratio provides background highlights that stand out clearly from the regular background
• the 3:1 ratio ensures that subdued text on highlighted background is ISO "standard" readable
• the 4½:1 ratio ensures that regular text on regular background is W3C "AA accessible" readable

The resulting colours:

seabird base colour	hex	hue °	saturation %	value %
seagrey1	0b141a	204	55	10
seagrey2	1d252b	204	34	17
seagrey3	61707a	204	21	48
seagrey4	6d767d	204	13	49
seagrey5	787e82	204	8	51
seagrey6	808487	204	5	53
seagrey7	e6eaed	204	3	93
seagrey8	ffffff	204	0	100

step 3: choosing accent colours

Accent colour hues were selected from around the (30°-divided) colour wheel: hue 204 plus seven companions.

colour	hue °	contrast level
red	354	high
orange	24	medium
yellow	54	low
green	114	low
teal	174	low
blue	204	medium
purple	264	high
pink	324	high

All hues were initially set to 100% saturation and value. Then:

• the low-contrast colours were reduced in value (yellow by ¼, green and teal by ⅓)
• the high-contrast colours were reduced in saturation (red by ¼, purple and pink by ⅓)
• the mid-contrast colours (orange and blue) were left alone

The goal contrast ratio was 3:1 (the ISO standard), prompting a few small hue adjustments.

seagull accent colour	hex	hue °	saturation %	value %
red	ff4053	354	75	100
orange	ff6200	23	100	100
yellow	bf8c00	44	100	75
green	11ab00	114	100	67
teal	00a5ab	182	100	67
blue	0099ff	204	100	100
purple	9854ff	264	67	100
pink	ff549b	335	67	100

For grey gull, each seagull accent colour was reduced in saturation by 38.2% (by applying the golden ratio), then reduced in value to a contrast ratio of 3:1.

grey gull accent colour	hex	hue °	saturation %	value %
red	db7681	354	46	86
orange	d1814f	23	62	82
yellow	ad9142	44	62	68
green	4aa840	114	62	66
teal	3fa2a6	182	62	65
blue	4e9bcf	204	62	81
purple	a783de	264	41	87
pink	cf7a9d	335	41	81

For petrel, each grey gull accent colour was reduced in value to a contrast ratio of 4½:1 (the W3C AA minimum).

petrel accent colour	hex	hue °	saturation %	value %
red	ba656d	354	46	73
orange	b06d43	23	62	69
yellow	947b38	44	62	58
green	3f8f36	114	62	56
teal	35898c	182	62	55
blue	4384b0	204	62	69
purple	8e6fbd	264	41	74
pink	b06886	335	41	69

For storm petrel, each petrel accent colour was reduced in saturation by 38.2% (by applying the golden ratio), then reduced in value to a contrast ratio of 4½:1.

storm petrel accent colour	hex	hue °	saturation %	value %
red	9e7276	354	28	62
orange	9c7760	23	38	61
yellow	8a7c55	44	38	54
green	5b8a55	114	38	54
teal	548587	182	38	53
blue	5f8299	204	38	60
purple	86779e	264	25	62
pink	997383	335	25	60

notes

The seabird colour scheme files are generated by modifying those of the flattened colour scheme by Romain Lafourcade, which is in turn derived from the Solarized colour scheme by Ethan Schnoonover.

Colour adjustment was performed with the GnuIMP colour selection tool. Contrast ratios were calculated with these formulas.

Actual contrast ratios may be slightly higher than those listed, due to discrete jumps in digital colour values.

Photo credits:

• seagull by Dan Hurt, petrel by Duncan (angrysunbird); both licensed CC BY-SA 2.0.
• 'fair weather sea' by Ali West, 'grey skies sea' by Mary (puzzlement); both licensed CC BY 2.0, both colour-adjusted