If you use the mobile Slack app, whether you work, school or play, you know that the background color in discussions about channels, threads and instant messages is white and that most of the text is black. Unlike the sidebar, there is no way to customize the colors shown here, but you have another option: dark mode.
Slack comes in two different color themes, light and dark. Light is the theme you are used to, with the white background and the black text. Dark is the newer colorant with higher contrast, which reverses these colors for an almost black dark gray background with some medium gray elements and light gray text. The darkness, which is sometimes called night mode, has several advantages over the light, which I am talking about later.
Dark mode was released for Android and iOS apps to Slack in March 2019, so before you go any further, make sure to update your Slack app to version 19.3.1 or later for iPhone or Android devices. If you are on Android and do not see the update yet, you can always sign up for the beta version to access directly.
Using Dark Mode on Slack
When you are on the right Slack version, tap the vertical ellipse (•••) at the top right and then select "Settings". If you are on an iPhone, then press the switch next to "Dark Mode". It will be in the third section after "Advanced".
On an Android phone, it's in the General section, but it's not a switch. Just press "Dark mode: Dark mode is disabled", and a pop-up menu may be displayed warning you that reboot is needed. If this is the case, press "Continue" and when the app is backed up, you get the darker theme.
After enabling "Dark Mode", changes are instantly displayed. You will see super dark gray and medium gray background throughout the app, the text will be light gray and the links will still be blue.
Images are not affected as in some inverted modes, so it here is the real deal.
First, it is easier when you read and write, especially in low light, so you do not get the darkening white to tighten your vision when you are in bed or upstairs. Second, it just looks cool, and it's another option apart from the standard, and customization is always welcome. Third, it can lower battery consumption on OLED screens.
When true blacks are used in dark mode, the pixels of these blacks are turned off and when you scroll, turn it on again. It sounds great, but you can get an inadvertent bleaching when you do it, so many dark modes hit the color a bit into a dark gray, improving the battery life of the OLED screens.
Something that is not affected by Slack's new dark mode is the sidebar. The background colors and font colors will be whatever you set, whether it's a default field like "Eggplant" (see below) or custom colors you've chosen.
If you want to get the dark theme in the sidebar as well, you need to design a custom theme with black or dark gray colors as background and light gray text. Just keep in mind that, unlike the dark mode, the sidebar theme changes over all Slack platforms – mobile apps, web sites and desktop apps.