data <- read.table("test.tab")

plot(data[,3]~data[,2], type="l", col="red",
ylim=c(-1,50), lty = 1,
main="Base percentage composition along reads",
xlab="Percent(%)",
ylab="Position along reads",
lwd=2)

lines(data[,4], type = "l", col="blue", lty=1, lwd=2)
lines(data[,5], type = "l", col="green", lty=2, lwd=2)
lines(data[,6], type = "l", col="orange",lty=2, lwd=2)
lines(data[,7], type = "l", col="black", lty=4, lwd=2)

legend("topright",
#legend=c("A","C","G","T","N"),
legend=c("A","T","C","G","N"),
#col=c("red","blue","green","orange","black"),
col=c("red","orange","blue","green","black"),
lty=c(1,2,1,2,4),lwd=2)