This feels wrong, I work in China in a European multinational with low number of Americans, yet we all spell in a mixture with no expectation of consistency: half the sentence can be in British, the rest in American and it will be an Australian reading the email and they will feel absolutely nothing: multi national corporations full of non-native speakers are completely used to the confusion. I'm French myself, I write color as often as I write colour, and practice and practise are completely identical to me.