Make it easier to distinguish the example and test states (do not rely only on color)

[girba]

Today, we only distinguish through color, but some people can have difficulties differentiating between colors. We should add visual shapes. The easiest initial step is to use:

• square for success
• triangle for failure
• circle for error

[girba]

[StephanEggermont]

Also the color coding needs a change: https://visualisingdata.com/2019/08/five-ways-to-design-for-red-green-colour-blindness/