BC-7654 - Colors: Update documentation (#37)

Update color documentation
* adjust color docs according to vuetify 3
* add part for "on" colors

docs/nuxt-client/7_Colors.md

@@ -3,85 +3,105 @@ sidebar_position: 8
 ---
 
 # Colors
+In the [Material Design system](https://m2.material.io/design/color/the-color-system.html) (the foundation of our component library), colors and color schemes are used to create a visual hierarchy, direct focus, and enhance the user experience.
 
-You can find our custom defined theme colors under `/src/themes/base-vuetify.options.js` and their overwrites per theme in `/src/themes/<theme_name>/vuetify.options.js`.
+You can find our custom defined theme colors under `/src/themes/base-vuetify.options.ts` and their overwrites per theme in `/src/themes/<theme_name>/vuetify.options.ts`.
 
-The colors vuetify provides you can find [here](https://v2.vuetifyjs.com/en/styles/colors/)
+You can find the colors provided by Vuetify [here](https://vuetifyjs.com/en/styles/colors/#colors).
 
 ## Usage
 
 ### Color Classes
 
-All colors defined by vuetify or in our vuetify options generate css classes you can use. To aplly a color variant like lighten1, add a second class like "grey lighten-1".
+All colors defined by Vuetify or in our Vuetify options generate CSS classes you can use. To apply a color variant like `lighten-1`, add it to the color like `grey-lighten-1`.
+Backgrounds have the `bg-`prefix and texts the `text-`prefix.
 
 #### Examples
 
-Using a color from vuetify's color palette:
+Using a color from Vuetify's color palette:
 
-```HTML
-<div class="blue">
+```html
+<div class="bg-blue">
   Blue background
 </div>
 ```
 
 Using a color defined in our vuetify options as text color:
 
-```HTML
-<p class="primary--text">
-  Blue background
+```html
+<p class="text-red">
+  Text has a red color
 </p>
 ```
 
-To use a variant of a color, you have to add a second class with the name of the variant:
+To use a variant of a color, you have to add the name of the variant seperated by hyphens:
 
-```HTML
-<p class="primary--text darken-1">
-  Blue background
+```html
+<p class="text-red-darken-1">
+   Text has a darken variant of the red color
 </p>
 ```
 
 ### Use Colors in (S)CSS
 
-For colors defined in our vuetify options, vuetify generates css variables.
+For colors defined in our Vuetify options, Vuetify generates CSS variables.
+Now, custom properties are an rgb list, so we need to use `rgba()` to access them.
 
 #### Examples
 
-```SCSS
+```scss
 .alert {
-  background-color: var(--v-secondary-darken1);
-  color: var(--v-white-base);
+  background-color: rgba(var(--v-theme-primary-lighten-1));
+  color: rgba(var(--v-theme-primary));
 }
 ```
 
-Colors from vuetify's colors palette (as of now) do not get generated css variables. You will need to access them with map-get.
+In Vuetify 2, we could only use hex values without the alpha property.
+With Vuetify 3, it's now possible:
 
-```SCSS
+```scss
+.example{
+  background-color: rgba(var(--v-theme-primary), 0.12);
+}
+```
+
+Colors from Vuetify's colors palette (as of now) do not get generated as CSS variables. You will need to access them with `map-get`.
+
+```scss
 .alert {
-  background-color: color: map-get($grey, base);;
-  color: color: map-get($blue, lighten-3);;
+  background-color: map-get($grey, base);
+  color: map-get($blue, lighten-3);
 }
 ```
 
-## Definition
+### "On-Surface" and "On-Background" Colors
+
+"On" colors are important for making text, icons, and other elements recognizable and readable on various backgrounds.
+
+- `on-surface`: Used for text, icons, and other elements that appear on top of a surface. Surfaces can include components like cards, dialogs, and menus.
+
+- `on-background`: Used for text, icons, and other elements that appear on the primary background of an application or a component
+
+We override the standard `on-surface` and `on-background` vuetify colors in our vuetify options and define them for each theme.
+
+## Definition Of Custom Colors
 
 You can define more custom colors in our vuetify options like this:
 
-```JS
+```typescript
 ...
-"icon-btn": {
- base: colors.grey.darken3,
-},
-"beta-task": {
- base: "#196C9E",
-},
+colors: {
+  info: "#0a7ac9",
+  "icon-btn": colors.grey.darken3,
+  "on-surface": "#0f3551",
+}
 ...
 ```
 
-As of now you can only use hex values without the alpha property. If a color is only meant for one theme only, please define the color in the relating theme file for our vuetify options.
-
 ### Rules
 
+- Talk to UX before introducing a new color
 - Do not overwrite vuetify colors
 - Use a semantic name to represent the use case
-- Prefer usage via map-get over new color definition, unless you introduce a new color
-- Either define style in template or in scss
+- Prefer usage via `map-get` over new color definition, unless you introduce a new color
+- Either define style in template or in SCSS