After logged into Tumblr click on the gear icon shown on the top right side of the page.
After that click on customize your blog (on the top right side of the page)
now here you can customize the text font size, and to change color click edit HTML, here you can change the text color but only advisable as basic HTML n CSS knowledge required.
You can also op text color change by changing the whole theme.
use a different theme
How to make your twitter sidebar invisible... http://louise-lloyd.com/geek/twitter-transparent-sidebar/
Simple, just click on Customise.
If you go to Tumblr's home page, it has a form for you to fill out to make an account with Tumblr.
Make the sidebar of a fixed length.
You can use the Whisper App to make facts on Tumblr.
to make the world more colourful.
Sign up for a new account make one and get on Tumblr.
It splits into the colours that make it up, so white light makes a rainbow, and different colours produce different results.
Minerals or purified salts (pigments)
I think you can make them different color by yourself. You can change different colors of cases for you ipad.
with a camera.