.NET のSystem.Windows.Media.Brushes の各プロパティの SolidColorBrush の色一覧を並べてみました。CSS3対応のブラウザで確認できると思います。

 
rgba(255,255,255,0)
Transparent
 
rgba(0,0,0,1)
Black
 
rgba(0,0,128,1)
Navy
 
rgba(0,0,139,1)
DarkBlue
 
rgba(0,0,205,1)
MediumBlue
 
rgba(0,0,255,1)
Blue
 
rgba(0,100,0,1)
DarkGreen
 
rgba(0,128,0,1)
Green
 
rgba(0,128,128,1)
Teal
 
rgba(0,139,139,1)
DarkCyan
 
rgba(0,191,255,1)
DeepSkyBlue
 
rgba(0,206,209,1)
DarkTurquoise
 
rgba(0,250,154,1)
MediumSpringGreen
 
rgba(0,255,0,1)
Lime
 
rgba(0,255,127,1)
SpringGreen
 
rgba(0,255,255,1)
Aqua
 
rgba(0,255,255,1)
Cyan
 
rgba(25,25,112,1)
MidnightBlue
 
rgba(30,144,255,1)
DodgerBlue
 
rgba(32,178,170,1)
LightSeaGreen
 
rgba(34,139,34,1)
ForestGreen
 
rgba(46,139,87,1)
SeaGreen
 
rgba(47,79,79,1)
DarkSlateGray
 
rgba(50,205,50,1)
LimeGreen
 
rgba(60,179,113,1)
MediumSeaGreen
 
rgba(64,224,208,1)
Turquoise
 
rgba(65,105,225,1)
RoyalBlue
 
rgba(70,130,180,1)
SteelBlue
 
rgba(72,61,139,1)
DarkSlateBlue
 
rgba(72,209,204,1)
MediumTurquoise
 
rgba(75,0,130,1)
Indigo
 
rgba(85,107,47,1)
DarkOliveGreen
 
rgba(95,158,160,1)
CadetBlue
 
rgba(100,149,237,1)
CornflowerBlue
 
rgba(102,205,170,1)
MediumAquamarine
 
rgba(105,105,105,1)
DimGray
 
rgba(106,90,205,1)
SlateBlue
 
rgba(107,142,35,1)
OliveDrab
 
rgba(112,128,144,1)
SlateGray
 
rgba(119,136,153,1)
LightSlateGray
 
rgba(123,104,238,1)
MediumSlateBlue
 
rgba(124,252,0,1)
LawnGreen
 
rgba(127,255,0,1)
Chartreuse
 
rgba(127,255,212,1)
Aquamarine
 
rgba(128,0,0,1)
Maroon
 
rgba(128,0,128,1)
Purple
 
rgba(128,128,0,1)
Olive
 
rgba(128,128,128,1)
Gray
 
rgba(135,206,235,1)
SkyBlue
 
rgba(135,206,250,1)
LightSkyBlue
 
rgba(138,43,226,1)
BlueViolet
 
rgba(139,0,0,1)
DarkRed
 
rgba(139,0,139,1)
DarkMagenta
 
rgba(139,69,19,1)
SaddleBrown
 
rgba(143,188,143,1)
DarkSeaGreen
 
rgba(144,238,144,1)
LightGreen
 
rgba(147,112,219,1)
MediumPurple
 
rgba(148,0,211,1)
DarkViolet
 
rgba(152,251,152,1)
PaleGreen
 
rgba(153,50,204,1)
DarkOrchid
 
rgba(154,205,50,1)
YellowGreen
 
rgba(160,82,45,1)
Sienna
 
rgba(165,42,42,1)
Brown
 
rgba(169,169,169,1)
DarkGray
 
rgba(173,216,230,1)
LightBlue
 
rgba(173,255,47,1)
GreenYellow
 
rgba(175,238,238,1)
PaleTurquoise
 
rgba(176,196,222,1)
LightSteelBlue
 
rgba(176,224,230,1)
PowderBlue
 
rgba(178,34,34,1)
Firebrick
 
rgba(184,134,11,1)
DarkGoldenrod
 
rgba(186,85,211,1)
MediumOrchid
 
rgba(188,143,143,1)
RosyBrown
 
rgba(189,183,107,1)
DarkKhaki
 
rgba(192,192,192,1)
Silver
 
rgba(199,21,133,1)
MediumVioletRed
 
rgba(205,92,92,1)
IndianRed
 
rgba(205,133,63,1)
Peru
 
rgba(210,105,30,1)
Chocolate
 
rgba(210,180,140,1)
Tan
 
rgba(211,211,211,1)
LightGray
 
rgba(216,191,216,1)
Thistle
 
rgba(218,112,214,1)
Orchid
 
rgba(218,165,32,1)
Goldenrod
 
rgba(219,112,147,1)
PaleVioletRed
 
rgba(220,20,60,1)
Crimson
 
rgba(220,220,220,1)
Gainsboro
 
rgba(221,160,221,1)
Plum
 
rgba(222,184,135,1)
BurlyWood
 
rgba(224,255,255,1)
LightCyan
 
rgba(230,230,250,1)
Lavender
 
rgba(233,150,122,1)
DarkSalmon
 
rgba(238,130,238,1)
Violet
 
rgba(238,232,170,1)
PaleGoldenrod
 
rgba(240,128,128,1)
LightCoral
 
rgba(240,230,140,1)
Khaki
 
rgba(240,248,255,1)
AliceBlue
 
rgba(240,255,240,1)
Honeydew
 
rgba(240,255,255,1)
Azure
 
rgba(244,164,96,1)
SandyBrown
 
rgba(245,222,179,1)
Wheat
 
rgba(245,245,220,1)
Beige
 
rgba(245,245,245,1)
WhiteSmoke
 
rgba(245,255,250,1)
MintCream
 
rgba(248,248,255,1)
GhostWhite
 
rgba(250,128,114,1)
Salmon
 
rgba(250,235,215,1)
AntiqueWhite
 
rgba(250,240,230,1)
Linen
 
rgba(250,250,210,1)
LightGoldenrodYellow
 
rgba(253,245,230,1)
OldLace
 
rgba(255,0,0,1)
Red
 
rgba(255,0,255,1)
Fuchsia
 
rgba(255,0,255,1)
Magenta
 
rgba(255,20,147,1)
DeepPink
 
rgba(255,69,0,1)
OrangeRed
 
rgba(255,99,71,1)
Tomato
 
rgba(255,105,180,1)
HotPink
 
rgba(255,127,80,1)
Coral
 
rgba(255,140,0,1)
DarkOrange
 
rgba(255,160,122,1)
LightSalmon
 
rgba(255,165,0,1)
Orange
 
rgba(255,182,193,1)
LightPink
 
rgba(255,192,203,1)
Pink
 
rgba(255,215,0,1)
Gold
 
rgba(255,218,185,1)
PeachPuff
 
rgba(255,222,173,1)
NavajoWhite
 
rgba(255,228,181,1)
Moccasin
 
rgba(255,228,196,1)
Bisque
 
rgba(255,228,225,1)
MistyRose
 
rgba(255,235,205,1)
BlanchedAlmond
 
rgba(255,239,213,1)
PapayaWhip
 
rgba(255,240,245,1)
LavenderBlush
 
rgba(255,245,238,1)
SeaShell
 
rgba(255,248,220,1)
Cornsilk
 
rgba(255,250,205,1)
LemonChiffon
 
rgba(255,250,240,1)
FloralWhite
 
rgba(255,250,250,1)
Snow
 
rgba(255,255,0,1)
Yellow
 
rgba(255,255,224,1)
LightYellow
 
rgba(255,255,240,1)
Ivory
 
rgba(255,255,255,1)
White