formation: update blue colors to USWDS v3 colors

[powellkerry]

Description

Update the current blue colors in formation to use the USWDS v3 colors. Color mappings are as follows:

//================
//  USWDS Colors
//===============
$color-aqua:                 #00bde3;
$color-aqua-dark:            #009ec1;
$color-aqua-lightest:        #e1f3f8;
$color-blue:                 #005ea2;
$color-blue-darkest:         #162e51;

$color-primary:              $color-blue;
$color-primary-darker:       #1a4480;
$color-primary-darkest:      $color-blue-darkest;

$color-primary-alt:          $color-aqua;
$color-primary-alt-light:    #97d4ea;
$color-primary-alt-lightest: $color-aqua-lightest;
$color-primary-alt-dark:     #28a0cb;

Issue link: department-of-veterans-affairs/vets-design-system-documentation#2228

Testing done

• Local testing on vets-website. I am wanting to publish a beta version of formation for additional local testing

Screenshots

Color change comparison:

Acceptance criteria

• [ ]

Definition of done

• Changes have been tested in vets-website
• Changes have been tested in IE11, if applicable
• Documentation has been updated, if applicable
• A link has been provided to the originating GitHub issue (or connected to it via ZenHub)
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs

[jamigibbs]

Formation uses USWDS v1 so a minor nit here would be that we mention this is USWDS v3 for clarity.