Allow usage of two-digit color codes

When using a two-digit color code, the two digits should be used as the same value for R, G and B.

For example:
- #13 has the same color result as #131313
- #f9 has the same color result as #f9f9f9
- #33 has the same color result as #333 and #333333
- #cc has the same color result as #ccc and #cccccc
- etc.