Pine Script-使用阶梯线和多色条件进行绘图

Question

为什么我可以根据断线或断线而不是分步线的条件来更改线条颜色？由于某些原因，当我使用stepline作为我的线条选项时，它会忽略条件并仅使用第一种颜色。有什么想法吗？

//@version=3 
study("My Script", overlay=true) 

lookback = input(title="Lookback Period", type=integer, defval=9, minval=1) 

HighestHigh = highest(close, lookback)[1] 
LowestLow = lowest(close, lookback)[1] 

highlinecolor = if HighestHigh > HighestHigh[1] 
 green 
else 
 if HighestHigh < HighestHigh[1] 
      red 
 else 
      gray 

lowlinecolor = if LowestLow > LowestLow[1] 
 green 
else 
 if LowestLow < LowestLow[1] 
      red 
 else 
      gray 

plot(HighestHigh, color=highlinecolor, linewidth=2, transp=0, title="Highest high", style=line) 
plot(LowestLow, color=lowlinecolor, linewidth=2, transp=0, title="Lowest Low", style=stepline)