I confess a personal interest in this, as it is my website for some research being carried out. But others can use it to find out their preferences. You can change the background colour, font colour, typeface, line spacing and even the gaps between letters. At the end you can print your results. If you fill in details we will be able to use your data as part of our research. (Details are not shared with anybody. But if you give us your email, it means you are happy to be invited to other research.)
Please note that there are other language versions in development, including Chinese and Portuguese. If you want to have your own language version, and are willing to collect data, please send me an email (firstname.lastname@example.org ).
Colour preferences - English
Colour preferences - Chinese