Your game will need to render two viewpoints, one for the left image and one for the right image. From there, a quick search revealed the following shader created by objo on Codeplex:
sampler2D input1 : register(S0); // right image input
sampler2D input2 : register(S1); // left image input
float4 main(float2 uv : TEXCOORD) : COLOR
Color1 = tex2D( input1 , uv.xy);
Color2 = tex2D( input2 , uv.xy);
Color1.r = Color2.r;
Color1.g = Color1.g;
Color1.b = Color1.b;
Color1.a = max(Color1.a,Color2.a);
While created for WPF applications, you might be able to use the above as-is or with a little bit of tweaking.
There have been many games from the NES on up that have rendered an anaglyphic or other method of 3d effect.
The above code is licensed under the CPOL
Link to Codeplex article: Anaglyph ShaderEffect in WPF