Correct python code for colour map X,Y scatter plot

I have a python program (uploaded). The aim of this program is to read in a text file of X,Y values and a colour intensity value (in column 4) and then to plot each point with a coloured square marker. The colour range should go from light yellow (for a value of 1) up to dark red. I am also uploading an input text file. If you run the code on this text file an output jpeg file will be produced. At the moment the program can read and plot ok - but the colours are wrong. For instance I noticed that a lot are too light. Perhaps some are too dark as well. I need some one to correct the colours to get the colouring 100% correct. But don't change the size of plot, axes, etc. I have an additional requirement. I want to be able to enter a value in the code that represents a colour clipping value. For instance, an input text file might have a minimum colour value of 1 and a maximum value of 1933. I want to be able to input any number (somewhere in the code) which would limit the top of the colour range to this number, eg I might choose 820, and this would then result in the colour range going from 1 to 820, with any points having values of 821 to 1933 all being the same as 820 (i.e. dark red). I think this is an easy task for someone who has done something similar in the past. I will only make one payment - once the program can correctly plot out a test dataset, which I will provide at the end. It will be very similar to the one uploaded at the start.