So I'm using my mum's old laptop since ltimage isnt compatible with my Chromebook :'( and uhh how do I add seperate colours because once i used it and it went entirely all purple.
We have instructions on 'Adding False Colour' to an image using LTImage on our website (link below). There's also a screencast showing how to do so.
If you have requested a 3-colour observation, you need to follow the instructions for 'Creating 3-colour images' on the same webpage.
I hope that helps.