How do I set a derma skin?

[A Fghtr Pilot]

(NOTE: I'm new to VGUI creation) So, how would I set a derma menu's skin to a black colour, instead of the default grey? I've tried to look up tutorials but I've found nothing. Also, how would I make a button that uses a .jpg file instead of a simple light grey button skin? I'm probably going to get boxes for asking this stuff, but I want to make a presentable, good-looking derma menu for a gamemode I'm making.

[RonanZer0]

[lua]function MyDermaPanel:Paint(w, h)
draw.RoundedBox(0, 0, 0, w, h, Color(0, 0, 0, 255));
end[/lua]

[A Fghtr Pilot]

What would I replace "MyDermaPanel" with? Well, for my code, I'm using

[lua]local DermaPanel = vgui.Create( "DFrame" )
DermaPanel:SetPos( 50,50 )
DermaPanel:SetSize( 200, 400 )
DermaPanel:SetTitle( "Class Selection" )
DermaPanel:SetVisible( true )
DermaPanel:SetDraggable( true )
DermaPanel:ShowCloseButton( true )
DermaPanel:SetDeleteOnClose( false )
DermaPanel:Hide()

local DermaButton = vgui.Create( "DButton", DermaPanel )
DermaButton:SetParent( DermaPanel ) -- Set parent to our "DermaPanel"
DermaButton:SetText( "Change to the Rifleman" )
DermaButton:SetPos( 25, 50 )
DermaButton:SetSize( 150, 50 )
DermaButton.DoClick = function()
RunConsoleCommand( "player_riflemanchange" )
end
DermaPanel.OnClose = function()
gui.EnableScreenClicker(false)
end

function GM:PlayerBindPress( ply, bind, pressed )
MsgN(bind)
if LocalPlayer() then
if ( string.find( bind, "menu_context" ) ) then
print(pressed)
if pressed then
DermaPanel:Show()
gui.EnableScreenClicker(true)
else
DermaPanel:Hide()
gui.EnableScreenClicker(false)
end
end
end
end
[/lua]

[RonanZer0]

[lua]function DermaPanel:Paint(w, h) // just replace DermaPanel with whatever vgui you wanna paint
draw.RoundedBox(0, 0, 0, w, h, Color(0, 0, 0, 255));
end[/lua]

You can also paint your buttons this way, and use [img]http://wiki.garrysmod.com/favicon.ico[/img] [url=http://wiki.garrysmod.com/page/draw/TexturedQuad]draw.TexturedQuad[/url] to draw an image instead of a RoundedBox.