skin.ini

Open skin.ini with something like notepad and examine each line.

As you can see some items have "Color" or "Clr" in it, these are 256 color definitions.
They are tagged in the HTML color format (Red, Green, Blue), your Paint program can show the color codes
For example:
FFFFFF = white
000000 = black
The numbers are from 0 to 256 in hexagonal value (0, 1,..., 8, 9, A, B, C, D, E, F)
So F = 16, FF = (16x16 = 256)
On every line after the "=" you may edit the value

Other lines show a ".bmp" which means they refer to painted images
The images may have any color depth ( 2 to 16 million colors), but keep in mind the more colors the more memmory it uses.
Open an image from the Default skin in your paint app and edit it.
Each image may have the size you want, now even the heights of PlayersPanel and AudioCtrlPanel
Here's an explanation list of each item:
FormThe mainwindow background color
FormTextThe default text color for mainwindow
ListColors of the playlist and database grids
ListArrowThe triangles shown in scrollbars of playlist and database
ListFixedColor of fixed row in playlist and database
ListSelectColor for selected rows in playlist and database
MP3Icon, OGGIcon, WAVIconImages for defining a MP3/OGG/WAV file in database
LeftIconImage in playlist that row is playing in left player
RightIconImage in playlist that row is playing in right player
PlayedIconImage in playlist that row is played
NotPlayIconImage in playlist that row won't be played
TalkBtnTalkover button
PlayersPanelBackground image players
AudioCtrlPanelBackground image crossfader
AutoXFadeColor for the "Automatic crossfade text"
PosLedPosition leds (below time counter)
VULedVolume leds
CuePointThumbThumb image for cue position (below position leds)
VolumeThumbThumb image for Volume sliders
PitchThumbThumb image for pitch sliders
EjectEject buttons
StopStop buttons
etc.etc.