Text colour changing on test emails

Text colour changing on test emails

I have put together a campaign e-mail I have altered the template and sent 3 different versions as test emails to various people in the office to see what they think, some people are receiving some emails with purple text (instead of black as set in the designs) but only one, and different emails for different people.

i.e.

person A has email 1 and 2 as black text but 3 as purple
person B has email 1 and 3 as black text but 2 as purple

can't seem to find a reason or solution to this, everyone is using Gmail on windows7.