@Anonymous
One way to get a darker colour is to call the ColorFade function.
Let's take the following main color: RGBA(204, 231, 246, 1)
To obtain a darker shade, you would call the following:
ColorFade(RGBA(204, 231, 246, 1),
-.05
)
The second argument (set to -0.5 above) dictates the darkness. You can set this between 0 and -1. A value of -1 will produce a shade that's completely black.