Change tags colour for all existing tags at ones, and set default tint for newly added Merged

We use a custom field (field type tag) to add customers to basically idea, features. As we need to visually distinguish between multiple tags (idea categories, customers, product components, ...), I want to change the colour of all existing tags at ones, instead of open all 300+ one after each other. Additionally, we'll add new tags on a daily basis, and it would be great to give those custom (tag) fields a default tint which will be taken when creating a new one.