Fix comments colours

[soshial]

Intellij Light (all are grey):

Argument 1:

According to the official documentation the comments should be of base1 colour #93a1a1:

Argument 2:

An example for Java(Vim) from the official documentation:

Before this PR change:

• different colours
• block comment colour is too similar to main text colour and is #657b83 which is base00 colour
• line comment is red for some reason

This PR changes to this:

• all comment colours have unified light grey look

[jkaving]

The comment colors was discussed quite a bit back in #67, #127, #152 and #155.

From #155:

To summarise it:

• Yes, it is intentional
• Javadoc comments are grey (or green, for Solarized Light) to be more unobtrusive
  This is a difference from the original Solarized theme where Javadoc comments are red
• Line comments are red - to stand out more (argued for in this article)

Perhaps a section about intentional differences from the original Solarized should be added to the README.