When checking your file, you may notice that there are other colours than CMYK called Spot colours. On Gelato, we recommend to change them into CMYK profile colour to avoid any issues with printing. Pantone shades/spot colours have the CMYK values defined, so you may check the CMYK values for a particular spot colour (Pantone shades) and apply them.
In order to find out if a spot colour is used in your InDesign document, please go to Windows > Output > Separation view in InDesign.
Once the below window appears, you will see the additional colours that need to be converted into CMYK, e.g. in the screenshot below that would be PANTONE S395 C.
1. Go to Window > Color > Swatches
2. Double click the spot colour that you need to convert to CMYK
3. In the tab Color type change 'Spot' option to 'Process' and click OK