title: ggplot line color "black" becomes red
body: <p>I used the following script to make the graph below</p>
  
  <pre><code>hypttauplot &lt;- qplot(fuclin_csf, fitHYPTTAU, data=selTAU, geom=c("smooth"),
                       method="glm", color='black', linetype=BL_HYPT) +
                 theme_classic() + xlab("Time (years)") + ylab("Tau (pg/ml)") +
                 scale_x_continuous(expand=c(0,0)) +
                 ggtitle("A. Hypertension") +
                 theme(legend.position = "none")
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/ZT3KI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZT3KI.png" alt="enter image description here"></a></p>
  
  <p>But now my questions is: why are the lines red instead of black? And how can I change them to black? </p>