English is spelled and pronounced differently in various parts of the world. For example, color is perfectly valid spelling in the US, but not so in the UK. And PowerPoint works different too depending upon which language settings have been specified — if your proofing language is set to English (UK), then the spell checker will suggest that the word color needs to be changed to colour. Clearly, the fact that PowerPoint adds red squiggly underlines to properly spelled words can be a nuisance — but that’s something you can rectify. In such situations you first need to have proofing tools installed for all or any of the languages that you need to work within PowerPoint.