changing colour in paint

ok before I shout at my computer, ive done this before on an older laptop but cant get it to work now....have scanned my original decal which as normal comes on a blue backing sheet, meaning when copying it before use, the blue is visible both behind and inside some of the decals..i know you can select a colour and replace it with another one (in this case blue with white) using eye dropper and eraser but cant get it to work at all for me now...either my memory has gone or new systems are different...any help appreciated..

Not something I'm familiar with Billy. It could be an older version of paint had more features.
Have tried it in Paint on my own machine and cant see an option for this. Most new machines come with some element of Photoshop installed these days which would be able to do what you need. With this installed, they may have removed some features to push Photoshop onto people.

ah that maybe explains it brian, cheers m8 for trying..