Hello there!
why in Dorico 3 some notes are indicated as out of range while they aren’t?
Example Bb4 on the trumpet.
Thank you

Can you be a bit more specific? I find that if I use a Trumpet in Bb at concert pitch, Dorico gives me this range (where red is considered “out of range” and crimson is considered appropriate only for advanced players).

Which trumpet are you adding to your project, and are you talking about concert pitch or transposed pitch, and is this a project that originated as imported MusicXML?

Dorico is often a bit too cautious with this marking, that’s true. Nothing prohibits you from writing those notes, though. Keep in mind that for your example, the note is coloured dark red, indicating “difficult but not impossible”, and bright red would actually mean impossible. If it bothers you, choose View>Note and Rest Colors>None.