Mode
Db Lydian
The Db Lydian mode (also written C#) — Db Eb F G Ab Bb C — shown across the guitar neck.
Also written C# Lydian. C# and Db are the same pitch, though spelling it from C# would need double accidentals (C# D# E# F## G# A# B#), which is why Db is the name in use.
Swipe the neck sideways to see the higher frets.
Db Lydian is the major scale with one note changed — the #4, G. That single note is what the mode sounds like; lean on it and the colour is obvious, avoid it and you are just playing major.
Notes
Db Eb F G Ab Bb C
Intervals
1 2 3 #4 5 6 7
Parent scale
Ab Major
Degree of parent
4
The tool shows this from its parent key, Ab major, with Db marked as where Lydian begins, the same seven notes centered on Ab.