ShaderToy (GLSL) - 147 bytes

void mainImage(out vec4 o,vec2 i){float x=i.x/iResolution.x*3.0;vec3 w=vec3(255,255,255);o=vec4((x<1.0?vec3(0,85,164):x<2.0?w:vec3(239,65,53))/w,1);}

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Not particularly exciting. I'm sure there are ways to golf it more; I'll take a crack when I get home.

ShaderToy (GLSL), 147 bytes

void mainImage(out vec4 o,vec2 i){float x=i.x/iResolution.x*3.0;vec3 w=vec3(255,255,255);o=vec4((x<1.0?vec3(0,85,164):x<2.0?w:vec3(239,65,53))/w,1);}

See it here

Not particularly exciting. I'm sure there are ways to golf it more; I'll take a crack when I get home.

ShaderToy (GLSL) - 156 bytes

void mainImage(out vec4 o,vec2 i){float x = i.x/iResolution.x*3.0;vec3 w=vec3(255,255,255);vec3 t=x<1.0?vec3(0,85,164):x<2.0?w:vec3(239,65,53);o=vec4(t/w,1);}

See it here

Not particularly exciting. I'm sure there are ways to golf it more; I'll take a crack when I get home.

ShaderToy (GLSL) - 147 bytes

void mainImage(out vec4 o,vec2 i){float x=i.x/iResolution.x*3.0;vec3 w=vec3(255,255,255);o=vec4((x<1.0?vec3(0,85,164):x<2.0?w:vec3(239,65,53))/w,1);}

See it here

Not particularly exciting. I'm sure there are ways to golf it more; I'll take a crack when I get home.

ShaderToy (GLSL) - 156 bytes

void mainImage(out vec4 o,vec2 i){float x = i.x/iResolution.x*3.0;vec3 w=vec3(255,255,255);vec3 t=x<1.0?vec3(0,85,164):x<2.0?w:vec3(239,65,53);o=vec4(t/w,1);}

See it here

Not particularly exciting. I'm sure there are ways to golf it more; I'll take a crack when I get home.

ShaderToy (GLSL) - 156 bytes

void mainImage(out vec4 o,vec2 i){float x = i.x/iResolution.x*3.0;vec3 w=vec3(255,255,255);vec3 t=x<1.0?vec3(0,85,164):x<2.0?w:vec3(239,65,53);o=vec4(t/w,1);}

See it here

Not particularly exciting. I'm sure there are ways to golf it more; I'll take a crack when I get home.