<script>
function zamow(){
var aaa = document.getElementById("aaa");
var ccc = document.getElementById("ccc");
var nnn = document.getElementById("nnn");
var r = document.getElementById("r");
var g = document.getElementById("g");
var b  = document.getElementById("b");
if (aaa.value==1) ccc.innerHTML="miś";
if (aaa.value==2) ccc.innerHTML="serce";
if (aaa.value==3) ccc.innerHTML="zaba";

// jeden sposób
nnn.style.backgroundColor = "#"+r.value+g.value+b.value;
// drugi sposób
nnn.style.backgroundColor = "rgb("+r.value+", "+g.value+", "+b.value+")";

}
</script>

<form method="post" action="">
  podaj nr krztałtu<br>
<input type="number" id="aaa"><br>
skomponuj swoj kolor<br>
  r:<input type="number" id="r">
  g:<input type="number" id="g">
  b:<input type="number" id="b">
  <br>
  <input type="button" value="zamów" onclick="zamow()">
  <br>
  <span id="ccc">wybierz krztałt</span>
  <br>
  <input type="button" value="wybrany kolor" id="nnn">
 
</form>