The only way to send colored text using the iPad is a third party app. You can send it using the Mail app, but you'll need a something else to create an HTML email. This is possible because while Mail does not provide HTML editing tools, it is capable of displaying HTML emails.
The only thin I have that will do this is Blog Docs. It's a kind of quirky app that lets you create HTML files in a WYSIWYG environment. The documents you create can be exported in a number of ways. For Mail, you can either copy and paste the parts you want into a new email (creating a snippet of colored text), or send the entire document as an email directly from the app.
Depending on what you want to do, this is either to much trouble, or a good tool.
Here is a fairly simple recipe template I created a few days ago. I just sent it to myself, and the screens hot is how it appears in my iMac's inbox; which is pretty much how it looks in the Blog Docs app and in Mail on the iPad.
There are other tools to do this, a few even targeted at the creation of email. This one is supposed to be (mostly) about blog posts. Search around and find the tool you want.
Edit: I tried copy and pasting some text from app to app, and could not make it work; though I know it has in the past. I was forced to start to send the document as an email, and then copy and paste the parts I wanted out of the body of the email in that app to the Mail app. That worked.
I did say the app was quirky.
