It's a small detail, but I think it's worth talking about briefly.
Simon is an audio-visual game. Each button has a color and a sound associated with it (that Симон abuses that rule doesn't change it). In the original Simon, the four sounds made a major chord (with the 4th note being an octave above the lowest). That made for happy sounds. Even recent Simon models use major triads for their sounds.
Симон, however is evil. So in keeping with its evil nature, the sounds are a diminished 7th chord. Each tone is a minor third away from its neighbor. It's the same chord (type) as the (in)famous Apple "sosumi" system sound. The four individual notes are C, E♭, G♭, B𝄫.
The sounds were made with GarageBand using a particularly pretty sounding chime instrument.