glcolor4ub in opengl es 2.0 - opengl-es-2.0

Question

I have some functions that use opengl to draw lines on the screen (health bars) and I recently moved from opengl es 1.1 to opengl es 2.0. I was using glColor4ub(50,160,50,255); to change the line color to green before rendering it on the screen, but that function appears to not exist in version 2.0. It says it is not valid and just renders all lines white.
Is there a different way I should be changing line colors? I've tried looking it up, but there doesn't seem to be anyone with the same question. It may be something simple I'm not seeing.
My game uses cocos2d 2.0 and the health bars are pretty much the only thing that I directly use opengl to render. Everything else is using sprite sheets and such. Thanks for any help.

Answer 1

As with everything else in OpenGL ES 2.0, you need to send the line colour to your fragment shader (via the vertex shader as a vertex attribute, or directly as uniform) and output the colour in your fragment shader.
In the simplest case, you could use a static value in the fragment shader:
void main(void) {
gl_FragColor = vec4(50.0/255.0, 160.0/255.0, 50.0/255.0, 255.0/255.0);
}
If you want to vary the colour at run time, send a value to the fragment shader as a uniform:
GLfloat color[4];
color[0] = 50.0/255.0;
color[1] = 160.0/255.0;
color[2] = 50.0/255.0;
color[3] = 255.0/255.0;
GLint lineColorSlot = glGetUniformLocation(shaderProgram, "LineColor");
glUniformMatrix4fv(lineColorSlot, 1, 0, color);
The fragment shader:
uniform lowp vec4 LineColor;
void main(void) {
gl_FragColor = LineColor;
}