Simple colours:
1. Write this code before the text you'd like coloured <*font color*=*color you prefer*>
2. Replace the "colour you prefer" with the colour that you prefer
3. Remove asterisks*

Example:
Gryffindor
Ravenclaw
Hufflepuff
Slytherin

Gradient:
Step 1. Go to this site: http://patorjk.com/text-color-fader/
Step 2. Type your text in the box
Step 3. Choose the colors you want (Or leave the rainbow)
Step 4. Click “Generate Color Faded Text”
Step 5. Copy paste the code in your backstory

Example:

Look like this!