In the future, whenever possible please post a packaged workbook with sample data so we can see what's going on and don't have to guess quite so much. There are three possibilities I can think of:
1) The pill on Color is a parameter and not a field. The workaround is to create a calculated field that has the parameter value and use that instead.
2) The pill on Color is a discrete (blue pill) measure whose values are being regularly updated so when ever the view refreshes the data changes and the color palette is adjusted. In this case the workaround is to either use a continuous (green) pill or to create a calculated field that uses IF/THEN or CASE statements to return categorical values that don't change every time the view is updated.
3) A Tableau bug. There's a historical bug on Tableau Server where views would occasionally lose their colors, there might be something like that happening.
If it's not one of these things then please post a packaged workbook with some sample data that demonstrates your problem.