Add zero prefix to individual rgb values so length of each values is always 2

[schmjop]

Description

Improve conversion from base 10 to base 16.

Related Issue

Motivation and Context

When converting rgb values <= 15 to hex, they only have a length of 1. E.g. "15 -> F".
This commit adds a prefix 0 for hex values with a length of 1.

How Has This Been Tested?

Testing different input values and and checking the output that is returned.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.