plugin for calculating white dot fraction on image?

[excalibur313]

Hi Everyone,
I am new to image-j and I have a series of orange images that have a bunch of white dots on them.  I would like to calculate the area of these white dots in relation to the entire image so I can have a fraction.  What would the appropriate plugin to be able to do this?  If possible, it would be also nice to have a range of light colors that would be accepted as "white" instead of straight 255 255 255.  Thank you so much for your help!