uniform float3 uniColor1;
uniform float3 uniColor2;
uniform float  uniFactor;

float4 main() : COLOR0
{
    float3 col = lerp(0.5, uniColor2, uniFactor); // should upcast 0.5 and uniFactor to float3
    float4 outcol = float4(col, 1);
    return lerp(0.5, float3(1), outcol); // should upcast to float4
}