ValueObject validation in CQRS Commands

[Chris-Mingay]

I've added a public string Colour property to CreateTodoListCommand and I process it as follows

The following API call for POST /api/TodoLists works as expected

Likewise if I were to post the exact same data again, I would get the following expected error

However when I attempt to POST with an invalid colour like the following ...

I get this response ...

This is understandable because the command doesn't check/catch the domain level validation error however it doesn't help the client consuming the API. A client might think they are presenting a valid colour string, however according to the domain it obviously isn't.

so my question is

How should I go about presenting ValueObject level validation errors in an Application level response?

Thank you

[Chris-Mingay]

My initial thoughts is to try and catch an exception

but I am not sure if that's sensible