[Vis colors] Replace observability default series color with ouiPaletteColorBlind()[0]

[joshuarrrr]

Observability visualizations define a default color as part of a color utility:

dashboards-observability/public/components/event_analytics/utils/utils.tsx

Lines 288 to 289 in 4ab8089

	// default color PLOTLY_COLOR[0]: '#3CA1C7'
	const defaultColor = [hex, '60', '161', '199'];

As part of #572, this default value should be updated to be the first color from ouiPaletteColorBlind(). It's also worth investigating whether the color utilities can be deprecated altogether in favor of OUI utilities, or moved to OUI.

see opensearch-project/oui#601 for visual comparison

[vvavdiya]

@mengweieric @joshuarrrr
I would like to look into issue incase any change is pending