How do I change the default color picker mode from HSV to RGB?

Question

Blender 2.8x default is HSV, but I want RGB like in 2.7x.

Saving startup file doesn't store new settings.

In the preferences settings one can only change circle to square or HSV to HSL, nothing more. No circle or square RGB

Answer 1

there is no option to change the color picker type to rgb

but you can download source of blender 2.83 and add an option to change colors to rgb

blender-2.83.5\source\blender\editors\interface_region_color_picker.c

Easy Solution

as you know enum has a default value

enum ePickerType {
  PICKER_TYPE_RGB = 0,
  PICKER_TYPE_HSV = 1,
  PICKER_TYPE_HEX = 2,
};

by default color picker type is PICKER_TYPE_HSV = 1

so you can change it to PICKER_TYPE_RGB = 0

 static char colormode = 0;

Hard Solution Adding to preferences

you should add a case for RGB in preferences

  switch (U.color_picker_type) {
    case USER_CP_SQUARE_SV:
      ui_colorpicker_square(block, ptr, prop, UI_GRAD_SV, cpicker);
      break;
    case USER_CP_SQUARE_HS:
      ui_colorpicker_square(block, ptr, prop, UI_GRAD_HS, cpicker);
      break;
    case USER_CP_SQUARE_HV:
      ui_colorpicker_square(block, ptr, prop, UI_GRAD_HV, cpicker);
      break;

    /* user default */
    case USER_CP_CIRCLE_HSV:
    case USER_CP_CIRCLE_HSL:
    case USER_CP_CIRCLE_RGB: # I ADD THIS CASE HERE
    default:
      ui_colorpicker_circle(block, ptr, prop, cpicker);
      break;
  }

there is a function to change the hsv/hsl to rgb:

void ui_color_picker_to_rgb(float r_cp0, float r_cp1, float r_cp2, float *r, float *g, float *b)
{
  switch (U.color_picker_type) {
    case USER_CP_CIRCLE_HSL:
      hsl_to_rgb(r_cp0, r_cp1, r_cp2, r, g, b);
      break;
    default:
      hsv_to_rgb(r_cp0, r_cp1, r_cp2, r, g, b);
      break;
  }
}

enum ePickerType {
  PICKER_TYPE_RGB = 0,
  PICKER_TYPE_HSV = 1,
  PICKER_TYPE_HEX = 2,
};

How does enum work?

 /* mode */
  yco = -1.5f * UI_UNIT_Y;
  UI_block_align_begin(block);
  bt = uiDefButC(block,
                 UI_BTYPE_ROW,
                 0,
                 IFACE_("RGB"),
                 0,
                 yco,
                 width / 3,
                 UI_UNIT_Y,
                 &colormode,
                 0.0,
                 (float)PICKER_TYPE_RGB,
                 0,
                 0,
                 "");

  UI_but_flag_disable(bt, UI_BUT_UNDO);
  UI_but_func_set(bt, ui_colorpicker_create_mode_cb, bt, NULL);
  bt->custom_data = cpicker;
  bt = uiDefButC(block,
                 UI_BTYPE_ROW,
                 0,
                 IFACE_((U.color_picker_type == USER_CP_CIRCLE_HSL) ? "HSL" : "HSV"),
                 width / 3,
                 yco,
                 width / 3,
                 UI_UNIT_Y,
                 &colormode,
                 0.0,
                 PICKER_TYPE_HSV,
                 0,
                 0,
                 "");

then you can use this function to change the color picker type:

bpy.context.preferences.view.color_picker_type = 'CIRCLE_RGB'

I also downloaded blender 2.79 source I found a function to convert rgb to hsv maybe useful:

2.79\scripts\addons\cycles\source\util\util_color.h

ccl_device float3 rgb_to_hsv(float3 rgb)
{
    float cmax, cmin, h, s, v, cdelta;
    float3 c;

    cmax = fmaxf(rgb.x, fmaxf(rgb.y, rgb.z));
    cmin = min(rgb.x, min(rgb.y, rgb.z));
    cdelta = cmax - cmin;

    v = cmax;

    if(cmax != 0.0f) {
        s = cdelta/cmax;
    }
    else {
        s = 0.0f;
        h = 0.0f;
    }

    if(s != 0.0f) {
        float3 cmax3 = make_float3(cmax, cmax, cmax);
        c = (cmax3 - rgb)/cdelta;

        if     (rgb.x == cmax) h =        c.z - c.y;
        else if(rgb.y == cmax) h = 2.0f + c.x - c.z;
        else                   h = 4.0f + c.y - c.x;

        h /= 6.0f;

        if(h < 0.0f)
            h += 1.0f;
    }
    else {
        h = 0.0f;
    }

    return make_float3(h, s, v);
}

Answer 2

Silly Solution

you can use a macro recorder to change the color type!!!

when you change the color type once it works for other colors until you close the blender

so use this program when you open the blender

import pyautogui

print(pyautogui.position())

pyautogui.moveTo(863,687,0.2) # Materil Position
pyautogui.click()
pyautogui.moveTo(976,677,0.2) # Color Position
pyautogui.click()
pyautogui.moveTo(834,559,0.2) # Change The Color Type to RGB
pyautogui.click()