R plotly-打印分组图表时如何固定颜色

我正在尝试使用plotly绘制重叠的直线图和条形图，并按相同的功能grp分组
我需要使用线和条的固定颜色

当我第一次添加条跟踪时，它运行良好：

library(plotly)

df <- data.frame(year = rep((2000:2017), each=2),
             grp = rep(c("Grp1", "Grp2"), 18),
             y1 = rnorm(36, 100, 40),
             y2 = rnorm(36, 50, 10)
             )


plot_ly(df) %>% 
   add_trace( x = ~year, y = ~y1, 
           type = 'bar', 
           yaxis = "y2",
           opacity = .4, 
           color = ~grp, 
           colors = colorRamp(c("grey", "black"))) %>%
   add_trace(x = ~year, y = ~y2, 
           type = 'scatter', 
           mode = 'lines+markers', 
           linetype = ~grp,
           line = list(color = "red")) %>% 
   layout(yaxis2 = list(overlaying = "y",
                     side = "right")) 

显然，我的语法是错误的：有人知道如何正确地编写此代码，以确保颜色稳定，无论顺序是什么吗

---

非常感谢

尝试在

绘图中指定
颜色
：

plot_ly(df, colors = colorRamp(c("grey", "black"))) %>% 
  add_trace(x = ~year, y = ~y2, 
       type = 'scatter', 
       mode = 'lines+markers', 
       linetype = ~grp,
       line = list(color = "red")) %>% 
  add_trace( x = ~year, y = ~y1, 
       type = 'bar', 
       yaxis = "y2",
       opacity = .4, 
       color = ~grp) %>%
  layout(yaxis2 = list(overlaying = "y",
       side = "right")) 

好的，谢谢。但我仍然不明白为什么切换add_line（）会有不同的输出。我想我用的方法不对，但什么是正确的方法？
plot_ly(df, colors = colorRamp(c("grey", "black"))) %>% 
  add_trace(x = ~year, y = ~y2, 
       type = 'scatter', 
       mode = 'lines+markers', 
       linetype = ~grp,
       line = list(color = "red")) %>% 
  add_trace( x = ~year, y = ~y1, 
       type = 'bar', 
       yaxis = "y2",
       opacity = .4, 
       color = ~grp) %>%
  layout(yaxis2 = list(overlaying = "y",
       side = "right"))