ggplot2 geom_jitter, colors

dotAW <- A_W_point
dotAW <- ggplot(dotAW,aes(x=AASW, y=WW, fill=taxa))  
dotAW <- dotAW  + geom_jitter(aes(color = taxa), size = 4)
dotAW <- dotAW  +geom_abline(intercept = 0, slope = 1)
dotAW <- dotAW + scale_y_continuous(limits=c(0,0.5)) + scale_x_continuous(limits=c(0,0.5))
dotAW

ggsave(dotAW, file="dotAW.pdf", width=12, height=10)

With this plot I want to correlate relative abundance of bacterial taxa. I have some issues to solve, where I need help

1. I want to change the color with eg + scale_fill_hue(l=45) or by creating my own color vector, but I don't know where to place it in the script, the colors are defined somehow connected to geom_jitter. In the end I want for each taxa an individual combination of color and shape to distinguish them in the plot easier than only using color.
2. I would like to define the dimension of the plot already before saving. Where and how can I add the height and width before?
3. Is the use of geom_jitter correct? It's a bit tricky for me to understand what it does.

here is a link to the data: https://docs.google.com/spreadsheets/d/1w5gHoWjFsgUUXEZOv9PTKfRQ-GyMkqulpAFVJaiX1K8/edit?gid=0#gid=0

With geom_jitter the point are plotted in their exact location, but somewhat besides that (above/below and/or right/left).

I've put your data in a dataframe df. Then you can create your plot with:

dotAW <- ggplot(df,aes(x=AASW, y=WW, color=taxa)) + 
  geom_point(shape = 20, size = 4, position = "jitter") +
  geom_abline(intercept = 0, slope = 1) + 
  scale_y_continuous(limits=c(-0.05,0.5)) + 
  scale_x_continuous(limits=c(-0.05,0.5)) +
  scale_color_hue()
dotAW

which gives the following result:

You can set the colors manually with scale_color_manual() like this:

scale_color_manual(values = c("Flavobacteriaceae"="red", "Oceanospirillales"="blue", "Gammaproteobacteria" = "green"))