Refine fringe-specific accented backgrounds

Meant to improve the performance of those colours in various relevant
scenaria.

The tables below show their relative luminance compared with
fg-main (the important one), bg-active, bg-inactive respectively.
Against fg-main the contrast must be >= 7:1 to conform with the WCAG AAA
standard.  The rest are offered as a comparison, with a value >= 1.3:1
considered passable (because the 7:1 applies to text, not whole blocks
which are easier to discern, plus it only concerns text directly on top
of a given background, not adjacent to it, as is the case with the
elements that would here be >= 1.3:1).

The new values are in the first section of the table.

Modus Operandi fringes new vs old
=================================

| Colour name       |        | 000000 | d7d7d7 | efefef |
|-------------------+--------+--------+--------+--------|
| red-fringe-bg     | f08290 |   8.30 |   1.76 |   2.20 |
| green-fringe-bg   | 62c86a |   9.99 |   1.46 |   1.83 |
| yellow-fringe-bg  | dbba3f |  11.11 |   1.31 |   1.64 |
| blue-fringe-bg    | 82afff |   9.53 |   1.53 |   1.92 |
| magenta-fringe-bg | e0a3ff |  10.85 |   1.34 |   1.68 |
| cyan-fringe-bg    | 2fcddf |  10.92 |   1.34 |   1.67 |
|-------------------+--------+--------+--------+--------|
| red-fringe-bg     | ff9a9a |  10.34 |   1.41 |   1.77 |
| green-fringe-bg   | 86cf86 |  11.28 |   1.29 |   1.62 |
| yellow-fringe-bg  | e0c050 |  11.83 |   1.23 |   1.54 |
| blue-fringe-bg    | 82afff |   9.53 |   1.53 |   1.92 |
| magenta-fringe-bg | f0a3ff |  11.39 |   1.28 |   1.60 |
| cyan-fringe-bg    | 00d6e0 |  11.69 |   1.25 |   1.56 |

Modus Vivendi fringes new vs old
================================

| Colour name       |        | ffffff | 323232 | 1e1e1e |
|-------------------+--------+--------+--------+--------|
| red-fringe-bg     | 8f1f4b |   8.52 |   1.51 |   1.96 |
| green-fringe-bg   | 006700 |   7.14 |   1.80 |   2.33 |
| yellow-fringe-bg  | 6f4f00 |   7.52 |   1.71 |   2.22 |
| blue-fringe-bg    | 3f33af |   9.11 |   1.41 |   1.83 |
| magenta-fringe-bg | 6f2f89 |   8.59 |   1.49 |   1.94 |
| cyan-fringe-bg    | 004f8f |   8.35 |   1.54 |   2.00 |
|-------------------+--------+--------+--------+--------|
| red-fringe-bg     | 8f0040 |   9.37 |   1.37 |   1.78 |
| green-fringe-bg   | 006000 |   7.86 |   1.63 |   2.12 |
| yellow-fringe-bg  | 6f4a00 |   7.91 |   1.62 |   2.11 |
| blue-fringe-bg    | 3a30ab |   9.59 |   1.34 |   1.74 |
| magenta-fringe-bg | 692089 |   9.68 |   1.32 |   1.72 |
| cyan-fringe-bg    | 0068a0 |   6.02 |   2.13 |   2.77 |

modus-operandi-theme.el

@@ -1171,10 +1171,10 @@ AMOUNT is a customisation option."
       ("magenta-active" . "#5c2092") ("cyan-active" . "#003f8a")
       ;; styles that are meant exclusively for the fringes
       ;;
-      ;; must be combined with `fg-main' or `fg-dim'
-      ("red-fringe-bg" . "#ff9a9a") ("green-fringe-bg" . "#86cf86")
-      ("yellow-fringe-bg" . "#e0c050") ("blue-fringe-bg" . "#82afff")
-      ("magenta-fringe-bg" . "#f0a3ff") ("cyan-fringe-bg" . "#00d6e0")
+      ;; must be combined with `fg-main'
+      ("red-fringe-bg" . "#f08290") ("green-fringe-bg" . "#62c86a")
+      ("yellow-fringe-bg" . "#dbba3f") ("blue-fringe-bg" . "#82afff")
+      ("magenta-fringe-bg" . "#e0a3ff") ("cyan-fringe-bg" . "#2fcddf")
       ;; styles reserved for specific faces
       ;;
       ;; `bg-hl-line' is between `bg-dim' and `bg-alt', so it should
@@ -1351,12 +1351,12 @@ Also bind `class' to ((class color) (min-colors 89))."
    `(modus-theme-nuanced-cyan ((,class :background ,cyan-nuanced-bg
                                        ,@(and (>= emacs-major-version 27) '(:extend t)))))
 ;;;;; fringe-specific combinations
-   `(modus-theme-fringe-red ((,class :background ,red-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-green ((,class :background ,green-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-yellow ((,class :background ,yellow-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-blue ((,class :background ,blue-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-magenta ((,class :background ,magenta-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-cyan ((,class :background ,cyan-fringe-bg :foreground ,fg-dim)))
+   `(modus-theme-fringe-red ((,class :background ,red-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-green ((,class :background ,green-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-yellow ((,class :background ,yellow-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-blue ((,class :background ,blue-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-magenta ((,class :background ,magenta-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-cyan ((,class :background ,cyan-fringe-bg :foreground ,fg-main)))
 ;;;;; special base values
    ;; these are closer to the grayscale than the accents defined above
    ;; and should only be used when the next closest alternative would be

modus-vivendi-theme.el

@@ -1171,10 +1171,10 @@ AMOUNT is a customisation option."
       ("magenta-active" . "#d5b1ff") ("cyan-active" . "#00d8b4")
       ;; styles that are meant exclusively for the fringes
       ;;
-      ;; must be combined with `fg-main' or `fg-dim'
-      ("red-fringe-bg" . "#8f0040") ("green-fringe-bg" . "#006000")
-      ("yellow-fringe-bg" . "#6f4a00") ("blue-fringe-bg" . "#3a30ab")
-      ("magenta-fringe-bg" . "#692089") ("cyan-fringe-bg" . "#0068a0")
+      ;; must be combined with `fg-main'
+      ("red-fringe-bg" . "#8f1f4b") ("green-fringe-bg" . "#006700")
+      ("yellow-fringe-bg" . "#6f4f00") ("blue-fringe-bg" . "#3f33af")
+      ("magenta-fringe-bg" . "#6f2f89") ("cyan-fringe-bg" . "#004f8f")
       ;; styles reserved for specific faces
       ;;
       ;; `bg-hl-line' is between `bg-dim' and `bg-alt', so it should
@@ -1351,12 +1351,12 @@ Also bind `class' to ((class color) (min-colors 89))."
    `(modus-theme-nuanced-cyan ((,class :background ,cyan-nuanced-bg
                                        ,@(and (>= emacs-major-version 27) '(:extend t)))))
 ;;;;; fringe-specific combinations
-   `(modus-theme-fringe-red ((,class :background ,red-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-green ((,class :background ,green-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-yellow ((,class :background ,yellow-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-blue ((,class :background ,blue-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-magenta ((,class :background ,magenta-fringe-bg :foreground ,fg-dim)))
-   `(modus-theme-fringe-cyan ((,class :background ,cyan-fringe-bg :foreground ,fg-dim)))
+   `(modus-theme-fringe-red ((,class :background ,red-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-green ((,class :background ,green-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-yellow ((,class :background ,yellow-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-blue ((,class :background ,blue-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-magenta ((,class :background ,magenta-fringe-bg :foreground ,fg-main)))
+   `(modus-theme-fringe-cyan ((,class :background ,cyan-fringe-bg :foreground ,fg-main)))
 ;;;;; special base values
    ;; these are closer to the grayscale than the accents defined above
    ;; and should only be used when the next closest alternative would be