@nico-ayala @nico-ayala
As part of FusionAuth, we do offer the option to theme on a per-application basis. So you could have a custom theme per application. This is a paid feature.
In FusionAuth users and application scope to a tenant. So, therefore:
instead of a multiple Tenant+single App?
This statement might have a bit more to unpack. Making more tenants to allow a new theme is possible, but this would entail that you have users logically separated per tenant (this might be fine; depends on your business use case). Sometimes, you have the same user base but have multiple applications that a user can log into. In this case, you might find that you want to have a new theme based on which brand/product/service (read: application) the user is logging into. In this case, you would use an application level theme override.
Additionally, please note below, following our documentation:
You apply a theme by configuring either a Tenant or an Application to use the theme. Each theme may apply to multiple Applications or Tenants; however, each Tenant or Application may have only one theme.
In sum, you can have the following
-Tenant A
--Application 1
--Application 2
-Tenant B
--Application 1
--Application 2
In this scenario, you could have a super-blue-and-great theme for Tenant A that Application 1 and Application 2 inherit. It is also equally possible to have Application 1 inherit this blue theme, but then have Application 2 have a super-green-and-great application level theme override for a new green-colored app that you are developing. To note, in this scenario, Tenant B and its "sub" applications will have their own themes and users.
I hope this helps!
Thanks,
Josh