Whether its a printable pdf version of a css/html coded webpage or you are just picking out a template for a web page or blog please consider this image below. Size is also a problem with text color and readability which is why I have posting the same image twice in two different size settings.
Full marks to everyone who noticed pale gray which I still see being used on some printable pdfs actually make the text look fuzzier at both sizes and all three colors! People try to remember some people make have printers set on black and white! Orange looks good on a screen but in print if the printer is low on colors ...? If you have a color printer try printing this out in color and in black and white to remind yourself or students about the need to to think about vieiwing sizes and how a document needs to work on screen and on paper.
I may do another text showing text colors in different popular font sizes.
Remember your design may be appearing on a mobile, tablet, laptop, large screen, or paper, on a standard A4 page or a poster? Test color and size.