Problem backgorund color opengl openframeworks

Hello everyone .I can not set a background color that I choose and I can not change the color of the particles that I created. Despite changing various colors I find myself always black. I am attaching here the source code so that you can help me. Thank you.

#include “ofApp.h”

void ofApp::setup(){

ofSetFrameRate(200);

int w=ofGetWidth();
int h=ofGetHeight();
fbo.allocate(w,h, GL_RGB32F_ARB);

fbo.begin();

ofBackground(ofColor::greenYellow);
fbo.end();

history=0.9;

time0=ofGetElapsedTimef();

emitter.setup();
}

//--------------------------------------------------------------
void ofApp::update(){

float time=ofGetElapsedTimef();
float deltaT= ofClamp(time-time0, 0, 6.0);

time0=time;

emitter.update();

}

//--------------------------------------------------------------
void ofApp::draw(){

ofBackground(ofColor::green);

fbo.begin();

emitter.draw();
fbo.end();

ofSetColor(ofColor::blanchedAlmond);
fbo.draw(0,0);
}