alpha blending in opengl es not working

alpha blending in opengl es not working

I'm trying to vary the transparency of a texture drawn onto a quad, the
code below works fine except the alpha set with glColor4f has no effect.
What are the possible reasons for this? Is it likely to be a gl setting
somewhere else in the program?

glEnable(GL_BLEND);
glBlendFunc(GL_SRC_COLOR, GL_ONE_MINUS_SRC_ALPHA);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textureId);
glColor4f(1.0f, 1.0f, 1.0f, 0.3f);
glVertexAttribPointer(vertexHandle, 3, GL_FLOAT, GL_FALSE, 0, quadVertices);
glVertexAttribPointer(normalHandle, 3, GL_FLOAT, GL_FALSE, 0, quadNormals);
glVertexAttribPointer(textureCoordHandle, 2, GL_FLOAT, GL_FALSE, 0,
quadTexCoords);
glEnableVertexAttribArray(vertexHandle);
glEnableVertexAttribArray(normalHandle);
glEnableVertexAttribArray(textureCoordHandle);
glUniformMatrix4fv(mvpMatrixHandle, 1, GL_FALSE,
(GLfloat*)&modelViewProjectionButton.data[0] );
glDrawElements(GL_TRIANGLES, NUM_QUAD_INDEX, GL_UNSIGNED_SHORT, quadIndices);
glDisableVertexAttribArray(vertexHandle);
glDisableVertexAttribArray(normalHandle);
glDisableVertexAttribArray(textureCoordHandle);