mock5 | Create and manage API mocks with Sinatra | REST library

I am trying to plot multiple lines in one ggplot in R using for loops. Currently, I don't believe I can use the melt() command to transition my data to long format due to some additional functionality I plan to add to the graphic down the road (filters, user inputs, etc. in a shiny dashboard - this will be my first dashboard, so please let me know if I am incorrect). I currently have the following code (see below) set up to assign a geom_line() command to a dynamic variable (produces x1 and x2). Next, I produce a vector of strings that tie to the dynamic variables created. The variable m is assigned as my ggplot() command. How do I create a plot that is the equivalent of m + x1 + x2 + scale_color_manual("red", "green") using the vector of strings to call the x# variables? Please note, this is for a QC process and over 200 variables need to be plotted in various graphs, so the solution needs to be scalable and not require me to explicitly type out each x# variable.