Some blocks like Paragraph and Button use inline styles. For various reasons we should avoid them and invent better system for styling blocks.

• Hard to maintain: Let's say we have hundreds buttons with my brand color. But then we re-design colors including button colors. It would be nasty job to change all previous button colors.
• Future-proof markup: Using !import is not an answer. It's also bad practise for modular, future-proof, and semantic separation of markup and presentation.
• Performance: Inline styles have small performance issue.
• Child themes: Child themes should be able to easily use different color combinations that parent theme.
• SEO: It's not good for SEO (don't ask me details, I don't know them:)
• In short, using inline styles has been considered as a bad practise for a long time.

Joe Dolson summarize it well:

Inline styles inhibit the ability of users to use their own custom stylesheets and create a barrier to tools that customize the view.

Proposal 1

I don't have a silver bullet but what if we start exploring how we could automate custom classes for blocks, something like bg-color-1, color-1, bg-color-2, color-2.

Example of current markup for paragraph:

<p style="background-color:#eee;font-size:28px;text-align:left" class="has-background has-drop-cap">
This is styled paragraph.
</p>

Example of markup for paragraph when we select first Background Color and Text color from Block settings:

<p class="has-background has-drop-cap bg-color-1 color-1">
This is styled paragraph.
</p>

Theme could map those styles to correct color what's declared in add_theme_support( 'gutenberg' ) and child themes could easily overwrite them.

Proposal 2

If nothing else theme should be able to disable inline styles. It could be done for example using 'inline-styles' => false, argument:

add_theme_support( 'gutenberg', array(
'wide-images' => true,
'inline-styles' => false,
'colors' => array(
	'#0073aa',
	'#229fd8',
	'#eee',
	'#444',
),
) );