Access to the web is a basic human right, meaning that anyone should be able to use and access sites on the web such as those we are building. There are common, low-hanging things you can do to make your website accessible:
Use a color-blind friendly color palette (or have options to enable a color-blind friendly mode). If you have access to people in your group that are colorblind, they may be a good litmus test for how colorblind-friendly your color palettes are.
Have alt-text on images to that those using screen readers, like the blind, will have images described to them
It's good to keep these things in mind from the beginning as it means you can hopefully avoid having to go back and make massive changes later after discovering something is completely unusable for a certain group.
The two points above are just the tip of the iceberg in terms of accessibility and there are many more things you can do to make your web application as accessible as possible. Below are more resources where you can learn more.
Here are some tools you can use to check basic accessibility and find low-hanging issues:
Most of this page is about making websites accessible. While command-line tools are generally accessible (plain text and don't depend heavily on colors), there are some things to avoid that are detailed in this Stackoverflow thread. In short, avoid only encoding important information via color and avoid ASCII art as it can interfere with screen readers.