The Modus themes are designed for accessible readability. They conform with the highest standard for color contrast between combinations of background and foreground values. For small sized text, this corresponds to the WCAG AAA standard, which specifies a minimum rate of distance in relative luminance of 7:1.
The Modus themes consist of eight themes, divided into four subgroups.
modus-operandi is the project’s main light theme,
while modus-vivendi is its dark counterpart. These two themes are
part of the project since its inception. They are designed to cover
a broad range of needs and are, in the opinion of the author, the
reference for what a highly legible “default” theme should look
like.
modus-operandi-tinted and modus-vivendi-tinted
are variants of the two main themes. They slightly tone down the
intensity of the background and provide a bit more color variety.
modus-operandi-tinted has a set of base tones that are shades of
light ocher (earthly colors), while modus-vivendi-tinted gives a
night sky impression.
modus-operandi-deuteranopia and its
companion modus-vivendi-deuteranopia are optimized for users with
red-green color deficiency. This means that they do not use red and
green hues for color-coding purposes, such as for diff removed and
added lines. Instead, they implement colors that are discernible by
users with deueteranopia or deuteranomaly (mostly yellow and blue
hues).
modus-operandi-tritanopia and its counterpart
modus-vivendi-tritanopia are optimized for users with blue-yellow
color deficiency. The idea is the same as with the deuteranopia
variants: color coding relies only on hues that are accessible to
people with tritanopia or tritanomaly, namely, shades of red and
cyan.
To ensure that users have a consistently accessible experience, the themes strive to achieve as close to full face coverage as possible, while still targeting a curated list of well-maintained packages (Face coverage).
The overarching objective of this project is to always offer accessible color combinations. There shall never be a compromise on this principle. If there arises an inescapable trade-off between usability and stylistic considerations, we will always opt for the former.
Starting with version 0.12.0 and onwards, the themes are built into GNU Emacs.