Disclaimer: I am not a lawyer. The following is not legal advice and, in particular, has not been tested in court to the best of my knowledge.
You can't use a different typeface, font size or color in a plain text document. That does not mean you have no options. The criterion is that it is “written, displayed, or presented that a reasonable person [...] ought to have noticed it.”
Consider the following:
Nihil harum autem impedit commodi ut occaecati. Nihil
quisquam ab molestiae veritatis consectetur. Quis molestias
sunt facere tempore est. Eum quia quisquam veritatis illo
minus sint atque ipsa. Omnis optio ducimus minus nemo non
deleniti voluptas. Blanditiis nisi eum eum beatae fugit
delectus. Optio neque sed nostrum veniam eos. Culpa ut no‐
bis rem est dignissimos est eum sed. Occaecati dignissimos
eveniet odit aut est ipsum minus nisi.
!! IMPORTANT !!
DISCLAIMER OF WARRANTY
The software is provided "as is", without warran‐
ty of any kind, express or implied, including but
not limited to the warranties of merchantability,
fitness for a particular purpose and noninfringe‐
ment. In no event shall the authors or copyright
holders be liable for any claim, damages or other
liability, whether in an action of contract, tort
or otherwise, arising from, out of or in connec‐
tion with the software or the use or other deal‐
ings in the software.
Unde sint ab qui ut. Debitis qui deserunt fugiat aut nihil
impedit vel saepe. Et ad voluptas quia. Omnis libero ni‐
hil perferendis aut ab. Illo et neque voluptatibus. Et
animi consequatur enim eius aut at veritatis. Modi error a
ratione tempore velit inventore. Accusantium accusantium
et quam quis nemo id.
This seems rather noticeable to me, gets to the point, and is considerably more readable.
By using the all-caps sparingly, we've made way to draw attention to the heading, then offset the passage with large amounts of whitespace to draw attention to the passage itself. At the same time, this keeps readability of the actual text that you want people to read.