Migrate GUI colors test to original CSS color format

[GuillaumeGomez]

Follow-up of #111459.

r? @notriddle

[notriddle]

@bors r+

[bors]

📌 Commit 5894193 has been approved by notriddle

It is now in the queue for this repository.

[bors]

⌛ Testing commit 5894193 with merge 5e8c53f...

[bors]

☀️ Test successful - checks-actions
Approved by: notriddle
Pushing 5e8c53f to master...

[bors]

☀️ Test successful - checks-actions
Approved by: notriddle
Pushing 5e8c53f to master...

[rust-timer]

Finished benchmarking commit (5e8c53f): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.5%	[0.5%, 2.5%]	4
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.4%	[-3.6%, -3.2%]	2
All ❌✅ (primary)	1.5%	[0.5%, 2.5%]	4

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.6%	[2.6%, 2.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.7%	[-4.7%, -2.7%]	2
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 648.528s -> 648.907s (0.06%)