Are we allowed to say mashaAllah about non-muslims or is that kufr?If for example my non muslim colleague is wearing a nice piece of jewellery is it permissible to say 'MashaAllah that is a pretty piece of jewellery' or for example to compliment a non-muslim by saying they are pretty or kind mashaAllah etc. If it is not permissible then don't we risk putting the eye on them?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.

It is not permissible to intentionally harm non-Muslims or give them the evil eye if they are under Thimmah (protection) status or peace treaty. If one sees something one likes about a non-Muslim, then the sanctioned act is to say "Mashaa’ Allaah" or a similar expression of admiration instructed by the Prophet, sallallaahu ʻalayhi wa sallam. This is because the property and life of such non-Muslim are protected in Islam, so it is not permissible to harm him as mentioned.

You thereby know that there is no harm in saying "Mashaa’ Allaah" upon seeing something that a non-Muslim, who is not at war with Muslims, possesses, and this does not constitute unbelief but is sanctioned as underlined above.

On the other hand, there is no harm in neglecting to say the prescribed Thikr (Mashaa' Allaah) when seeing something one likes that a  belligerent non-Muslim possesses, even if it incurs harm on him or causes him to be deprived of such a blessing, because his life and property are not protected by Islam.

You should also know that there is no harm in praising and admiring the good qualities of non-Muslims as long as it does not lead to anything prohibited in Sharee'ah, such as loving them or making forbidden alliances with them. Allaah The Exalted described some of the People of the Book as being honest and honoring trusts, saying (what means): {And among the People of the Scripture is he who, if you entrust him with a great amount [of wealth], he will return it to you.} [Quran 3:75]

It does not necessarily follow from simply describing them in the manner mentioned in the question that one envies them or has given them the evil eye.

Allaah Knows best.