How do I randomly pick every color from my array only once without using classes

For my assignment I have to create the game 'memory'. I keep getting stuck on the part where I randomly give every card a color.

I first created this array

int rectColorArray[] ={BROWN, BROWN,WHITE, WHITE,RED, RED, GREEN, GREEN};

And made a loop in wich I hoped it would only pick each color once.

void drawCards(int rectColor){
  int length = 50;
  int xPos =0;
  int yPos =0;

  for(int i = 7; i >= 0; i--){
    rectColor = rectColorArray[(int)random(0,rectColorArray.length)];
    fill(rectColor);
   rect(xPos,yPos, length, length); 
   xPos = xPos + length + 10;   
    splice(rectColorArray,i,1);
  }
}

it seems as if 'splice' doesn't do anything, because I keep getting rects that doesn't give the wanted output.

So my final question is: Does anyone know how to fix this problem, or if I should use another technique.