# Changing colours

**URL:** <https://forums.buildingsmart.org/t/changing-colours/2704>\
**Category:** Uncategorized\
**Created:** [May 15, 2020, 11:25am UTC](https://forums.buildingsmart.org/t/changing-colours/2704 "2020-05-15T11:25:21Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![pilarjimenez](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/pilarjimenez/32/407_2.png) [@pilarjimenez](https://forums.buildingsmart.org/u/pilarjimenez)\
**Post date:** [May 15, 2020, 11:25am UTC](https://forums.buildingsmart.org/t/changing-colours/2704/1 "2020-05-15T11:25:21Z")

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I’m just trying to do a quick test.

When open an ifc and search for colour y get some lines as this one:

#188 = IFCCOLOURRGB($, 3.76470588235E-1, 3.76470588235E-1, 3.76470588235E-1);

As Ifc defines the colour as RGB and the definition from ISO10303-46, we can’t see colours in rgb as (255, 102, 057).

Ok, my cuestion is this:

- first: i want to recognize this colour in an online palette
- second: i want to choose another colour an get it in this system for changing the #188 line.  
.  
Anyone knows this online tool? I only get conversion tools to hexadecimal and cymk. Maybe is as simple as a mathematical formula but a tool with colour selector will be more usefull  
Thank you in advance

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**Author:** ![TLiebich](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/tliebich/32/71_2.png) [@TLiebich](https://forums.buildingsmart.org/u/TLiebich)\
**Post date:** [May 15, 2020, 12:09pm UTC](https://forums.buildingsmart.org/t/changing-colours/2704/2 "2020-05-15T12:09:44Z")

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IFC stores RGB colours as a range of 0 … 1, see:  
[https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2\_TC1/HTML/link/ifccolourrgb.htm](https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/ifccolourrgb.htm)

Converted into the common 2by8 range of 0 … 255, it would mean that 0 equals 0, and 1 equals 255. The conversion is simply n x 255 =\> 0 x 255 = 0, and 1 x 255 = 255.

So your colors are:  
R = 0.376470588235 x 255 = 96  
G = 0,376470588235 x 255 = 96  
B = 0.376470588235 x 255 = 96

so it should be a dark grey. The conversion is easy to do in Excel.

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<div class="post-metadata">

**Author:** ![pilarjimenez](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.buildingsmart.org/pilarjimenez/32/407_2.png) [@pilarjimenez](https://forums.buildingsmart.org/u/pilarjimenez)\
**Post date:** [May 15, 2020, 3:05pm UTC](https://forums.buildingsmart.org/t/changing-colours/2704/3 "2020-05-15T15:05:36Z")

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Thank you Thomas

I was looking at the ifcolour definition in last 4.1 published version:

[https://standards.buildingsmart.org/IFC/DEV/IFC4\_3/RC1/HTML/link/ifccolour.htm](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC1/HTML/link/ifccolour.htm)