DrawPrimitives::setDrawColor4B alpha is not woking

cocos2d-x C++
#1

cocos2d-x 3.2

[how to draw alpha line]DrawPrimitives::setDrawColor4B alpha is not woking?

my code: DrawPrimitives::setDrawColor4B(255,0,0,0);, alpha = 0 is show the line, how to show alpha = 0.1 line

void GameStageLayer_Level_1_0::draw(Renderer *renderer, const Mat4 &transform, uint32_t flags)
{
_customCommand.init(_globalZOrder);
_customCommand.func = CC_CALLBACK_0(GameStageLayer_Level_1_0::onDraw, this, transform, flags);
renderer->addCommand(&_customCommand);
}

void GameStageLayer_Level_1_0::onDraw(const Mat4 &transform, uint32_t flags)
{

//return;

Director* director = Director::getInstance();
director->pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);
director->loadMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW, transform);

CHECK_GL_ERROR_DEBUG();


{
         float width_line = 5.0f;

    DrawPrimitives::setDrawColor4B(255,0,0,255*1.0/100.0); 
    glLineWidth( width_line );
#2

i fix it:

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);