要使用vcl样式更改选项卡的字体颜色，必须覆盖Vcl.ComCtrls.TTabControlStyleHook样式钩子的DrawTab方法，并使用自己的代码绘制选项卡并设置颜色字体.

To change the font color of a tabsheet using the vcl styles, you must override the DrawTab method of the Vcl.ComCtrls.TTabControlStyleHook style hook and use your own code to draw the tab and set the color font.

尝试此示例

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ComCtrls;

type
  TForm1 = class(TForm)
    PageControl1: TPageControl;
    TabSheet1: TTabSheet;
    TabSheet2: TTabSheet;
    TabSheet3: TTabSheet;
    TabSheet4: TTabSheet;
    TabSheet5: TTabSheet;
    TabSheet6: TTabSheet;
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

uses
  Vcl.Styles,
  Vcl.Themes;

{$R *.dfm}

type
  TTabFontColorStyleHook= class(Vcl.ComCtrls.TTabControlStyleHook)
  protected
    procedure DrawTab(Canvas: TCanvas; Index: Integer); override;
  end;

  TWinControlClass = class(TWinControl);
  TCustomTabControlClass = class(TCustomTabControl);


procedure TTabFontColorStyleHook.DrawTab(Canvas: TCanvas; Index: Integer);
var
  LDetails    : TThemedElementDetails;
  LImageIndex : Integer;
  LThemedTab  : TThemedTab;
  LIconRect   : TRect;
  R, LayoutR  : TRect;
  LImageW, LImageH, DxImage : Integer;
  LTextX, LTextY: Integer;
  LTextColor    : TColor;

    procedure DrawControlText(const S: string; var R: TRect; Flags: Cardinal);
    var
      TextFormat: TTextFormatFlags;
    begin
      Canvas.Font       := TWinControlClass(Control).Font;
      TextFormat        := TTextFormatFlags(Flags);
      Canvas.Font.Color := LTextColor;
      StyleServices.DrawText(Canvas.Handle, LDetails, S, R, TextFormat, Canvas.Font.Color);
    end;

    procedure AngleTextOut2(Canvas: TCanvas; Angle, X,
      Y: Integer; const Text: string);
    var
      LSavedDC: Integer;
    begin
      LSavedDC := SaveDC(Canvas.Handle);
      try
        SetBkMode(Canvas.Handle, TRANSPARENT);
        Canvas.Font.Orientation := Angle;
        Canvas.TextOut(X, Y, Text);
      finally
        RestoreDC(Canvas.Handle, LSavedDC);
      end;
    end;

begin
  if (Images <> nil) and (Index < Images.Count) then
  begin
    LImageW := Images.Width;
    LImageH := Images.Height;
    DxImage := 3;
  end
  else
  begin
    LImageW := 0;
    LImageH := 0;
    DxImage := 0;
  end;

  R := TabRect[Index];
  if R.Left < 0 then Exit;

  if TabPosition in [tpTop, tpBottom] then
  begin
    if Index = TabIndex then
      InflateRect(R, 0, 2);
  end
  else if Index = TabIndex then
    Dec(R.Left, 2) else Dec(R.Right, 2);

  Canvas.Font.Assign(TCustomTabControlClass(Control).Font);
  LayoutR := R;
  LThemedTab := ttTabDontCare;
  //Get the type of the active tab
  case TabPosition of
    tpTop:
      begin
        if Index = TabIndex then
          LThemedTab := ttTabItemSelected
        else if (Index = HotTabIndex) and MouseInControl then
          LThemedTab := ttTabItemHot
        else
          LThemedTab := ttTabItemNormal;
      end;
    tpLeft:
      begin
        if Index = TabIndex then
          LThemedTab := ttTabItemLeftEdgeSelected
        else if (Index = HotTabIndex) and MouseInControl then
          LThemedTab := ttTabItemLeftEdgeHot
        else
          LThemedTab := ttTabItemLeftEdgeNormal;
      end;
    tpBottom:
      begin
        if Index = TabIndex then
          LThemedTab := ttTabItemBothEdgeSelected
        else if (Index = HotTabIndex) and MouseInControl then
          LThemedTab := ttTabItemBothEdgeHot
        else
          LThemedTab := ttTabItemBothEdgeNormal;
      end;
    tpRight:
      begin
        if Index = TabIndex then
          LThemedTab := ttTabItemRightEdgeSelected
        else if (Index = HotTabIndex) and MouseInControl then
          LThemedTab := ttTabItemRightEdgeHot
        else
          LThemedTab := ttTabItemRightEdgeNormal;
      end;
  end;

  //draw the tab
  if StyleServices.Available then
  begin
    LDetails := StyleServices.GetElementDetails(LThemedTab);//necesary for  DrawControlText
    StyleServices.DrawElement(Canvas.Handle, LDetails, R);
  end;

  //get the index of the image (icon)
  if Control is TCustomTabControl then
    LImageIndex := TCustomTabControlClass(Control).GetImageIndex(Index)
  else
    LImageIndex := Index;

  //draw the image
  if (Images <> nil) and (LImageIndex >= 0) and (LImageIndex < Images.Count) then
  begin
    LIconRect := LayoutR;
    case TabPosition of
      tpTop, tpBottom:
        begin
          LIconRect.Left := LIconRect.Left + DxImage;
          LIconRect.Right := LIconRect.Left + LImageW;
          LayoutR.Left := LIconRect.Right;
          LIconRect.Top := LIconRect.Top + (LIconRect.Bottom - LIconRect.Top) div 2 - LImageH div 2;
          if (TabPosition = tpTop) and (Index = TabIndex) then
            OffsetRect(LIconRect, 0, -1)
          else
          if (TabPosition = tpBottom) and (Index = TabIndex) then
            OffsetRect(LIconRect, 0, 1);
        end;
      tpLeft:
        begin
          LIconRect.Bottom := LIconRect.Bottom - DxImage;
          LIconRect.Top := LIconRect.Bottom - LImageH;
          LayoutR.Bottom := LIconRect.Top;
          LIconRect.Left := LIconRect.Left + (LIconRect.Right - LIconRect.Left) div 2 - LImageW div 2;
        end;
      tpRight:
        begin
          LIconRect.Top := LIconRect.Top + DxImage;
          LIconRect.Bottom := LIconRect.Top + LImageH;
          LayoutR.Top := LIconRect.Bottom;
          LIconRect.Left := LIconRect.Left + (LIconRect.Right - LIconRect.Left) div 2 - LImageW div 2;
        end;
    end;
    if StyleServices.Available then
      StyleServices.DrawIcon(Canvas.Handle, LDetails, LIconRect, Images.Handle, LImageIndex);
  end;

  //draw the text of the tab
  if StyleServices.Available then
  begin

    //here you set the color of the font
    LTextColor:=clRed;

    if (TabPosition = tpTop) and (Index = TabIndex) then
      OffsetRect(LayoutR, 0, -1)
    else
    if (TabPosition = tpBottom) and (Index = TabIndex) then
      OffsetRect(LayoutR, 0, 1);

    if TabPosition = tpLeft then
    begin
      LTextX := LayoutR.Left + (LayoutR.Right - LayoutR.Left) div 2 - Canvas.TextHeight(Tabs[Index]) div 2;
      LTextY := LayoutR.Top + (LayoutR.Bottom - LayoutR.Top) div 2 + Canvas.TextWidth(Tabs[Index]) div 2;
      Canvas.Font.Color := LTextColor;
      AngleTextOut2(Canvas, 900, LTextX, LTextY, Tabs[Index]);
    end
    else
    if TabPosition = tpRight then
    begin
      LTextX := LayoutR.Left + (LayoutR.Right - LayoutR.Left) div 2 + Canvas.TextHeight(Tabs[Index]) div 2;
      LTextY := LayoutR.Top + (LayoutR.Bottom - LayoutR.Top) div 2 - Canvas.TextWidth(Tabs[Index]) div 2;
      Canvas.Font.Color := LTextColor;
      AngleTextOut2(Canvas, -900, LTextX, LTextY, Tabs[Index]);
    end
    else
     DrawControlText(Tabs[Index], LayoutR, DT_VCENTER or DT_CENTER or DT_SINGLELINE  or DT_NOCLIP);
  end;
end;



initialization
  TStyleManager.Engine.RegisterStyleHook(TCustomTabControl, TTabFontColorStyleHook);
  TStyleManager.Engine.RegisterStyleHook(TTabControl, TTabFontColorStyleHook);
end.

这就是结果

还存在一些资源，当您需要使用vcl样式自定义标签页和页面控件组件时，这些资源可以为您提供帮助.

Also exist several resources which can help you when you need customize a tabsheet and pagecontrol components using vcl styles.

• Creating colorful tabsheets with the VCL Styles
• 在TTabColorControlStyleHook中添加了边框
• 检查 vcl样式实用程序项目.
• 如何更改主题TabSheet的文本颜色字幕?

• Creating colorful tabsheets with the VCL Styles
• Added border to TTabColorControlStyleHook
• Check the code of the Vcl.Styles.ColorTabs unit, which is part of the vcl styles utils project.
• How can i change text color of themed TabSheet caption?