Android/OpenGL ES2: How do I set fragment shader value using C;

Android/OpenGL ES2: How do I set fragment shader value using C;

This should be easy So I am using the following to create a fragment shader.
 GLbyte fShaderStr[] = "precision mediump float;"
    "void main()                                \n"
    "{                                          \n"
    "  gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0); \n"
    "}                                          \n";
I then render a circle (collection of lines) the circle comes our red. If I change the code to...
GLbyte fShaderStr[] = "precision mediump float;"
    "void main()                                \n"
    "{                                          \n"
    "  gl_FragColor = vec4(1.0, 0.0, 1.0, 1.0); \n"
    "}                                          \n";
The circle is now purple. My question is how do I control this dynamically? So for example when I receive an input I toggle the two colors?
I tried...
GLbyte vShaderStr[] = "attribute vec4 vPosition;   \n"
            "attribute vec4 inColor;   \n"
    "uniform mat4 Projection;   \n"
    "varying vec4 fragColor;   \n"
    "void main()                 \n"
    "{                           \n"
    "   gl_Position = Projection * vPosition; \n"
    "   fragColor = inColor; \n"
    "}                           \n";

GLbyte fShaderStr[] = "precision mediump float;"
    "varying vec4 fragColor;                   \n"
    "void main()                                \n"
    "{                                          \n"
    "  gl_FragColor = fragColor; \n"
    "}\n";


void initColor(){
    LOGD("Initing Color");
    GLfloat vVertices[] = { 1.0f, 0.0f, 0.0f, 1.0f };
    glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, vVertices);
}
However, this doesn't seem to work as the circle is now black.