If you really mean litmus paper, blue and or red, you will not be able to tell much.
If you mean pH paper, with a range of 1 to 14, you will not be able to tell much.
If you mean pH paper, with a range of 6.0 to 8.0 you will have a crude approximation, but the color differences are still very hard to discern.
Your best bet is bromothymol blue with a known kH solution and a drop checker.
http://www.greenleafaquariums.com/co...-checkers.html
Or a decent pH test kit such as a hach phenol red:
http://www.hach.com/hc/search.product.details.invoker/VendorProductCode=1251900/View=PRODUCT_OVERVIEW/NewLinkLabel=pH+Test+Kit%2C+Color+Cube%2C+6.5-8.5+pH%2C+50+tests/SESSIONID|Amt4TWpJNU56TTVORGN5TkRFMUptZDFaWE4wV2to RlZnPT1CRg==|