Hull MA Color Modification

Hi, Can you color code the Hull EMA? Uptrend - Green and Downtrend - Red. Something like this...
input price = close;
input length = 20;
input displace = 0;

plot HMA = MovingAverage(AverageType.HULL, price, length)[-displace];

HMA.DefineColor("Up", GetColor(1));
HMA.DefineColor("Down", GetColor(0));
HMA.AssignValueColor(if HMA > HMA[1] then HMA.color("Up") else HMA.color("Down"));