onlyggifiwin

Hue/Saturation did the trick but I forgot to mention that I wanted to be able to pick a specific colour if there were multiple, such as in the image attached. This was solved using Hue / Saturation Plus. Edit: Recolour choice was found to be more convenient.

For the image below, is there a way for me to change the colour of all the purple lines without changing each of them individually i.e. in 1 go?

I ended up using AHK to remap my delete key to send Shift + Backspace. Disabling anti-aliasing did not work.

I want it to behave like Microsoft Paint where deleting just makes the selection turn white. I don't want delete to turn the selection area into a transparent area. This is because when I use the image in a pdf, I get annoying boxes like such