The newly refreshed Royal Blue design includes updated link colors. Previously it looked like this

It was incredibly obvious and clear to the user which had and hadn't been clicked yet. Now it looks like this

Everything blends together so much that I can't tell what has and hasn't been clicked at a glance. Moon Dark doesn't have this issue, but I'd prefer to use Royal Blue as it otherwise looks nicer.

For now I've restored the previous link behavior by copying the old .theme_dark CSS variables from a cached browser session into the custom CSS. Provided below in case anyone else is similarly struggling:
.theme_dark_conditional { --cheatsh_background:#22242f; --cheatsh_ef186:#d7d787; --cheatsh_ef15:#FDF6E3; --cheatsh_ef148:#afd700; --cheatsh_ef81:#5fd7ff; --color-scheme:dark; --background-color:#262837; --background-color-dim_3:rgba(38, 40, 55, 0.3); --background-color_opac:rgba(38, 40, 55, 0); --page-text-color:#e5e5e5; --beta-tag-bg:#4835bc; --beta-tag-text:#f2f0e7; --beta-tag-inside-corners:#9debfe; --login_page_bg:#171820; --login_page_divider_strap:#42435c; --kagi-sky:#42435c; --kagi-sky-b:#13131e; --login_page_input_bg:#161820; --kagi-accent:#1d1f29; --kagi-graphite-s:#535353; --kagi-graphite-ia:#ffb319; --kagi-graphite-ia-color:#191919; --color-primary:rgb(229, 229, 229); --color-secondary:rgb(25, 25, 25); --color-primary-dim_1:rgba(229, 229, 229, 0.1); --color-primary-dim_2:rgba(229, 229, 229, 0.2); --color-primary-dim_25:rgba(229, 229, 229, 0.25); --color-primary-dim_3:rgba(229, 229, 229, 0.3); --color-primary-dim_3_solid:#434551; --color-primary-dim_4:rgba(229, 229, 229, 0.4); --color-primary-dim_5:rgba(229, 229, 229, 0.5); --color-primary-dim_6:rgba(229, 229, 229, 0.6); --color-primary-dim_7:rgba(229, 229, 229, 0.7); --color-primary-dim_8:rgba(229, 229, 229, 0.8); --color-primary-dim_9:rgba(229, 229, 229, 0.9); --color-primary-g:rgb(229, 229, 229); --color-primary-dim-g_2:rgba(229, 229, 229, 0.2); --color-primary-dim-g_6:rgba(229, 229, 229, 0.6); --color-primary-dim-g_8:rgba(229, 229, 229, 0.8); --color-secondary-dim_1:rgba(25, 25, 25, 0.1); --color-secondary-dim_2:rgba(25, 25, 25, 0.2); --color-secondary-dim_4:rgba(25, 25, 25, 0.4); --color-secondary-dim_5:rgba(25, 25, 25, 0.5); --color-secondary-dim_6:rgba(25, 25, 25, 0.6); --color-secondary-dim_7:rgba(25, 25, 25, 0.7); --color-secondary-dim_8:rgba(25, 25, 25, 0.8); --color-secondary-dim_9:rgba(25, 25, 25, 0.9); --color-search-input-opac:rgba(38, 40, 55, 0); --color_link:#9debfe; --color-primary_hover:#9debfe; --color-primary_visited:#deb6f1; --input-bg:#161820; --resultsummary-highlight:#9debfe; --resultsummary-highlight_text:var(--color-secondary); --bangs_tag_bg:var(--color-primary); --doggo-color-1:#e5e5e5; --doggo-bg-color:#383b50; --landing-page-clouds-opacity:0.8; --quick-search-bg:#ffffff; --quick-search-icon:#4835bc; --tabs-round-bg:#1d1f29; --tabs-round-active-bg:rgba(66, 70, 103, 0.25); --color_cat_buttons:var(--color-primary-dim_7); --color_cat_buttons_active:var(--color-secondary); --color_cat_buttons_bg:var(--color-primary); --color_cat_buttons_border:var(--color-primary-dim_2); --color_cat_buttons_border_hover:var(--color-primary-dim_5); --header-bg:#1f1d2c; --header-bg-opac:rgba(31, 29, 44, 0); --app-logo:#191919; --app-logo-bg:#ffb319; --footer-bg:#151515; --control-center-dd-bg:#161820; --control-center-dd-bg_hover:#161820; --control-center-dd-list:#161820; --control-center-dd-list-bg_hover:#1d1f29; --control-center-bg:#1f1d2c; --control-center-dd-border:#43465b; --filter-dd-bg:#161820; --cc-filters-active-bg:#404040; --k-tooltip-bg:var(--color-primary); --k-tooltip-text:var(--color-secondary); --dd-hover-bg:#1d1f29; --dd-list-input-bg:#24262e; --not-found-bubble-bg:var(--color-secondary); --app-sidebar-bg:#1f1d2c; --app-sidebar-item-border:rgba(229, 229, 229, 0.1); --app-sidebar-link:var(--color-primary-dim_5); --app-sidebar-nav-item-bg_hover:#ffb319; --app-sidebar-nav-item-link_hover:var(--app-sidebar-bg); --app-sidebar-nav-item-icon_hover:var(--color-primary); --app-sidebar-lense-link:var(--color-primary-dim_5); --app-sidebar-lense-link_hover:#ffffff; --ranked-box-overlay-bg:rgba(18, 18, 18, 0.9); --ranked-box-wrapper-bg:#262837; --ranked-box-connection-secure:#60aa55; --ranked-box-connection-insecure:#fd6820; --ranked-box-icon-normal-bg:var(--ranked-box-wrapper-bg); --ranked-box-tracker-no-info:#7d7d7d; --ranked-box-toggle-switch-ch1-text:var(--color-primary); --ranked-box-toggle-switch-ch3-svg-bg:var(--color-secondary); --ranked-box-settings-btn-bg:var(--ranked-box-wrapper-bg); --rank-icon-shard-color:#a1a1a1; --rank_icon_boosted:#ffb319; --site_info_bg:#262837; --site_info_bottom_bg:#1f1d2c; --site_info_grad_normal_1:#1992d6; --site_info_grad_normal_2:#08f784; --site_info_grad_trackers_1:#6415a2; --site_info_grad_trackers_2:#007cff; --site_info_grad_trackers_danger_1:#f76c08; --site_info_grad_trackers_danger_2:#9f1414; --btn-group-bg:#1f1d2c; --result-item-title-border:rgba(229, 229, 229, 0.5); --result-item-title-border_hover:rgba(68, 77, 165, 0.5); --result-rank-icon-stroke_promoted:var(--background-color); --k-tooltip-tracker_bg:#333; --result-item-highlight:#9debfe; --search-result-content-text:var(--color-primary-dim_6); --search-result-group-item-link:var(--color-primary-dim_9); --search-result-url-link:var(--color-primary-dim_9); --search-result-title:#ffffff; --search-result-date-bg:rgba(66, 70, 103, 0.25); --search-result-date-new-bg:#424667; --search-result-date-new:#e5e5e5; --inline-header-title:#ffffff; --inline-widget-bg:#212433; --inline-header-border:rgba(229, 229, 229, 0.5); --inline-domain-tag-bg:rgba(66, 70, 103, 0.25); --related-item-bg:#1d1f29; --username-button-bg:var(--inline-widget-bg); --ranked-tabs-border:var(--color-primary-dim_2); --video-item-bg:#191919; --auto-sugg-bg_hover:rgba(229, 229, 229, 0.05); --provider-breakdown_server:#075067; --provider-breakdown_client:#9b6400; --provider-breakdown_speed1:#6f6d22; --provider-breakdown_speed2:#ab5a5a; --provider-breakdown_speed3:#812503; --widget-progress_bar:#e5e5e5; --translate-fc_icon:#777676; --rating-star_background:#666666; --wiki-title:#ffffff; --wiki-content-links:#ffffff; --toggle-switch-knob-bg:#262837; --m_sri_gap_color:#1f1d2c; --image_brightness:85%; --onboarding_theme_options_dark_visibility:flex; --onboarding_theme_options_light_visibility:none; --onb_theme_light_preview_box:none; --onb_theme_calm_blue_preview_box:none; --onb_theme_royal_blue_preview_box:block; --onb_theme_moon_dark_preview_box:none; --billing-svg-bg-premium_1:var(--inline-widget-bg); --result_favicon_pos_theme_light:none; --result_favicon_pos_theme_calm_blue:none; --result_favicon_pos_theme_royal_blue:block; --result_favicon_pos_theme_dark:none; --result_url_style_theme_light:none; --result_url_style_theme_calm_blue:none; --result_url_style_theme_royal_blue:block; --result_url_style_theme_dark:none; --maps-highlight:#161820; --code-bg:#282c34; --code-border:#4d4d4d; --code-k:#e06c75; --code-s:#e5c07b; --code-cm-c1:#fd6820; --code-n:#61afef; --code-p:#e06c75; --plan-free-bg:#363748; --plan-standard-bg:#363a50; --plan-team-bg:#4b5a7e; --onb_plan_switch_bg:#6481b3; --kids_cloud_stars_fill:unset; --kids_landing_bg_grad:#121212; --ai_chat_buble_a_bg:#16171c; --ai_chat_buble_q_bg:#1d1f29; --ai_chat_buble_dd_a_bg:#191a21 }

I'm using Firefox Developer Edition 125.0b9 on Windows 10. The behavior is exactly the same on Brave so I don't believe this is browser-specific.